Method of identifying positions of wheel modules

ABSTRACT

There is provided a method of identifying locations of modules ( 400 ) of an apparatus ( 600, 680, 690, 2200 ) for monitoring wheels ( 10 ) of a vehicle ( 900 ). The sensor modules ( 400 ) operatively revolving with the wheels ( 10 ). The modules ( 400 ) communicate with a processing arrangement ( 710 , ECU  950 ) of the vehicle ( 900 ). The modules ( 400 ) sense a physical parameter of the wheels ( 10 ) and generate corresponding sensor signals for the processing arrangement ( 950 ). The processing arrangement ( 710 , ECU  950 ) processes the sensor signals to compute information indicative of operation of the wheels ( 10 ). The apparatus ( 1 ) also includes a sensor arrangement ( 118 ) for sensing an angular orientation ( 0 ) of the wheels ( 10 ). The method includes steps of: (b) arranging an elongate feature ( 1100 ) in an at least partially transverse direction relative to a direction of travel of the vehicle ( 900 ); (c) driving the vehicle ( 900 ) over the elongate feature ( 1100 ) to cause the wheels ( 10 ), together with their associated modules ( 400 ), to contact momentarily onto the elongate feature ( 1100 ) and communicating signals including signal components stimulated by contact of the wheels ( 10 ) onto the elongate feature ( 1100 ) to the processing arrangement ( 950 ), the signals identifying a time at which their wheels ( 10 ) contacted onto the elongate feature ( 1100 ) and identification codes (ID) of the modules ( 400 ); and (d) from a temporal sequence of the signals received at the processing arrangement ( 950 ), identifying whereat modules ( 400 ) are located on the wheels ( 10 ) of the vehicle ( 900 ).

FIELD OF THE INVENTION

The present invention relates to methods of identifying positions ofwheel modules included in wheels and/or their associated tyres; forexample, to a method of identifying positions of wheel modules operableto monitor characteristics of wheels and/or their associated tyres andconveying information indicative of these aforementioned characteristicsvia a communication link to an electronic control unit (ECU) and/orcontrol system, for example for user-display. Moreover, the presentinvention also concerns wheel modules for use in implementingaforementioned methods. Additionally, the invention relates to methodsof servicing vehicles including such wheel modules. Furthermore, thepresent invention also relates to software and software productsexecutable on computing hardware for executing these aforesaid methods.

BACKGROUND OF THE INVENTION

Tyres, also known as “tires” in American-English, are criticalcomponents in road vehicles. Contemporary tyres not only ensure adhesionof their associated road vehicles to road surfaces in widely varyingweather conditions, but also perform vibration and shock isolationfunctions. Moreover, during their operating lifetime, tyres are requiredto survive potentially up to several thousand or even millions ofdeformation cycles without exhibiting work-hardening failure, and yetexhibit a relatively modest degree of energy dissipation therein as aresult of viscous dampening effects. As an additional operatingrequirement, contemporary tyres need to be robust against scuffing andobjects impacting thereonto. Yet further, tubeless tyres are required torobustly grip onto their associated wheel hubs even when subject toconsiderable stresses, for example during emergency braking. In responseto these aforementioned requirements for contemporary tyres, the tyresare constructed from elastic synthetic rubber, natural rubber and/orplastics material reinforced by meshes of metal wire, carbon fibre andsimilar. Modern tyres are therefore to be respected as highly optimizedand advanced products.

Tyre failure during operation can potentially result in immobilizationof an associated vehicle or even accident. Moreover, tyres operated atunsuitable pressures can adversely influence associated vehicle fueleconomy; fuel economy is becoming increasingly pertinent in view ofincreases in fuel costs as well as in view of carbon dioxide generationand its perceived impact on World climate change.

It is known to mount sensors onto automobiles to monitor characteristicssuch as tyre pressure and acceleration in one or more orthogonal axes,and to convey information representative of these characteristics viawireless communication links to electronic control units (ECU) formingparts of data management systems of the vehicles. By employing sucharrangements, it is possible to warn drivers of a need to inflate one ormore tyres of their vehicles in order to improve driving quality andsafety.

In a published Japanese patent no. JP 2003211924 (Mazda Motor), there isa disclosed a pneumatic sensor device suitable for use with a tyre of avehicle for detecting tyre pressure and generating corresponding tyrepressure information. The device includes a transmitter for transmittingthe pressure information together with an identification code fordistinguishing the sensor device from other such sensor devicessimultaneously included on other wheels of the vehicle. A control unitof the vehicle is operable to receive the transmitted pressureinformation and its associated identification code. The receivedpressure information is stored in a memory of the control unit. Thecontrol unit is operable to raise an alarm in an event that tyrepressure is not correct pursuant to predefined criteria.

In a published United Kingdom patent application no. GB 2385931 A, tyremonitors are described which are mounted adjacent to tyres near theirtyre inflation valve stems. The tyre monitors include sensors to measurepressure, temperature and rotation direction of their respective tyres.Moreover, the monitors are operable to communicate measured sensorsignals via transmitters to their respective receiver for subsequentprocessing and eventual presentation on a display unit. A vehiclemounted controller in communication with the receiver is operable todetermine whether pressure information is associated with a front tyreor a rear tyre based on the strength of the wireless signal received atthe receiver, and whether pressure data is associated with a right tyreor left tyre based on associated rotation direction data.

On account of tyre condition being an important factor influencingvehicle operating economy and safety, a technical problem is thereforehow to provide more advanced wheel and tyre monitoring. When a fleetoperator has many vehicles in its fleet, ensuring quality of wheel andtyre maintenance for all the vehicles in the fleet is paramount. Suchquality can at least partially be ensured by following rigorous manualmaintenance routines, for example by performing regular vehicleinspections and systematically changing tyres after a predefined numberof traveled kilometers. However, it is still feasible that tyres andwheels undergo events which escape the attention of such rigorousmaintenance routines and can therefore represent a potential hazard. Forexample, wheels are potentially exchanged between vehicles eitherwithout authorization of respective vehicles owners which can therebycircumvent such rigorous maintenance routines or by way of theft.Moreover, wheel hubs are susceptible over their operating lifetime tobeing provided with numerous replacement tyres.

As elucidated in the foregoing, tyre monitors are known. In order tomeasure tyre condition and detect unauthorized tampering with tyres, forexample when wheels are temporarily removed from their associatedvehicles, for example when exchange from winter tyres to summer tyres inNorthern Europe and Canada, more advanced tyre and wheel monitors arerequired. However, there then arises a technical problem regarding howto manage complex configurations of tyre and wheel monitors, especiallywhen tyres are replaced at mutually different times and wheels and theirtyres are susceptible to being retained in storage over periods whenexchanging between summer and winter tyres.

The present invention seeks to address the aforementioned technicalproblems.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved method ofidentifying locations of wheel and/or tyre monitors included inapparatus of vehicles which is capable of enhancing safety andreliability of such vehicles.

This object is addressed by a method according to the first aspect ofthe invention as defined in appended claim 1. There is provided a methodof identifying locations of one or more modules of an apparatus includedin a vehicle for monitoring operation of at least one wheel of thevehicle, the one or more modules operatively mounted to revolve with theat least one wheel, the one or more modules being operatively coupled incommunication with a processing arrangement (ECU) of the vehicle, theone or more modules being operable to sense at least one physicalparameter of the wheel and to generate at least one corresponding sensorsignal for the processing arrangement, the processing arrangement (ECU)being operable to process the at least one sensor signal to computeinformation indicative of operation of the at least one wheel,

characterized in that the method includes steps of:

-   (a) arranging for at least one elongate feature to be provided in an    at least partially transverse direction relative to a direction of    travel of the vehicle;-   (b) driving the vehicle over the elongate feature to cause the at    least one wheel, together with its associated one or more modules,    to contact momentarily onto the elongate feature and communicating    signals including signal components stimulated by contact of the at    least one wheel onto the elongate feature to the processing    arrangement, the signals identifying a time at which their at least    one wheel contacted onto the elongate feature and one or more    identification codes (ID) of the one or more modules mounted onto    the at least one wheel; and-   (d) from a temporal sequence of the signals received at the    processing arrangement, identifying locations whereat the one or    more modules are located on the one or more wheels of the vehicle.

The invention is of advantage in that it provides a simple practicalmethod of identifying the locations whereat the one or more modules ofthe apparatus are located on wheels of the vehicle.

By “elongate feature” is meant any feature which is susceptible tocausing signals to be generated from the one or more modules similar tothat generated from such an elongate feature.

Optionally, when implementing the method, the apparatus includes asensor arrangement for sensing an angular orientation (θ) of the atleast one wheel.

Optionally, when implementing the method, the signals are indicative ofat least one of:

-   (e) one or more components of acceleration (A_(x), A_(y)) sensed at    the at least one wheel; and-   (f) a pressure sensed in a tyre of the at least one wheel.

Optionally, when implementing the method, the vehicle is driven at thepartially transverse angle so as to result in signals from the one ormore modules being temporally mutually different between correspondingleft-hand-side and right-hand-side wheels of the vehicle, therebyenabling the processing arrangement to distinguish locations whereat theone or modules along the vehicle and distinguish whether the one or moremodules are on a left-hand side or a right-hand side of the vehicle, inthe event the overall direction of the elongate is known, such thatinformation is available of which side of the elongated feature isexpected to generate a signal first. From such information, that is ifthe elongated feature is inclined from the left to the right side,having the left side closer to the vehicle, or vice versa, informationof an expected temporal separation between an impact of the wheels onthe left and right sides respectively can be established. The respectivesensor modules arranged on the left and right sides can therefore beidentified by the temporal separation of the received input signals fromthe modules. The overall direction of the elongated feature can beknown, either by using a test rig where the direction of the elongatedfeature is known, or by use of a road monitoring system which by imagerecognition can identify an elongated object and determine a generaldirection of the elongate feature with respect to the vehicle.Preferably the inclination of the elongate feature is selected so thatthe temporal separation between wheels arranged on the left and rightside is smaller than the temporal separation between wheels arranged ondifferent axes of the vehicle. By studying the geometry of the vehicleand identifying the distance between a left and right tyre arranged onthe same axle and comparing it with a distance between two axles of thevehicle which are closest to each other a suitable limit for theinclination of the elongated feature can be selected. Normally the limitcan be selected to be less than 45° for a vehicle having two axles orless than 30° for vehicles having three or more axles. Around 15-20°would provide for a suitable separation between left and right andseparation between each axle for a vehicle having three axles. Selectionof an appropriate inclination for an elongated feature arranged in atest rig is straight forward. The road monitoring system can be arrangedto determine the inclination of an identified elongated feature withrespect to a heading direction of the vehicle. The system may then beallowed to perform the method according to this invention only when theinclination of the detected elongated feature is within a selectedappropriate range.

Optionally, when implementing the method to provide pseudo-continuousmonitoring or continuous monitoring of the at least one wheel, themethod is implemented repetitively whilst the vehicle is being driven innormal use.

Optionally, the method includes an additional step of identifying thoseone or more modules (400) mounted to a wall (230) or onto an inside rimof a tyre (30) of the at least one wheel (10) by identifying periodicpulses (500) in acceleration signal components (A_(y), A_(z)) derivedfrom the one or more modules (400) corresponding to rotation of the atleast one wheel (10).

According to a second aspect of the invention, there is provided awheel-monitoring apparatus operable to execute a method pursuant to atleast one of the first, second and third aspects of the invention.

According to a third aspect of the invention, there is provided a moduleoperable to function in a vehicle for implementing a method pursuant toat least one of the first, second and third aspects of the invention.

According to a fourth aspect of the invention, there is provided avehicle including a wheel-monitoring apparatus pursuant to the fourthaspect of the invention, the apparatus being operable to monitoroperation of at least one wheel (10) of the vehicle (900) pursuant to amethod of at least one of the first, second and third aspects of theinvention.

According to a fifth aspect of the invention, there is provided a wheelincluding one or more modules mounted thereonto, the one or more modulesoperable to function with a wheel-monitoring apparatus pursuant to thefourth aspect of the invention operable to monitor operation of at leastone wheel of the vehicle pursuant to at least one of the first, secondand third aspects of the invention.

According to an sixth aspect of the invention, there is provided a tyreincluding a module as pursuant to the fifth aspect of the invention.

Optionally, the module is mounted to a side wall or adjacent athread-section of the tyre.

When the aforementioned apparatus has been “calibrated” pursuant to atleast one of the first, second and third aspects of the invention,namely positions of one or more modules identified, the apparatus isoperable to provide wheel and tyre monitoring. An additional technicalproblem then pertains how best utilize information provided from theapparatus for maintaining the vehicle operational in service.

This additional technical problem is at least partially addressed by thepresent invention.

According to a seventh aspect of the present invention, there isprovided a system including one or more vehicles, wherein each vehicleincludes a wheel-monitoring apparatus operable to execute a methodpursuant to at least one of the first, second and third aspects of theinvention, the system comprising:

-   (a) a control centre for coordinating repair or maintenance of the    one or more vehicles;-   (b) one or more service facilities operable to perform repair or    replacement on the one or more vehicles;    wherein the system is operable to:-   (c) enable each wheel-monitoring apparatus to monitor operation of    its one or more associated wheels and detect when a problem or    potential problem arises therewith;-   (d) enable each wheel-monitoring apparatus to communicate the    problem or potential problem to the control centre, for the control    centre to identify one or more service facilities capable of    addressing the problem or potential problem; and-   (e) enable the control centre to communicate instructions to the one    or more vehicles whose wheel-monitoring apparatus has detected a    problem or potential problem to the identified one or more service    facilities for the problem or potential problem to be addressed.

Optionally, the system in (e) is operable to inform the identified oneor more service facilities in advance of arrival of the one or morevehicles for maintenance or repair, so that the identified one or moreservice facilities are provided with an opportunity to make preparationfor arrival of the one or more vehicle for maintenance or repair.

Optionally, when implementing the system, the control centre is operableto organise the maintenance or repair at the identified one or moreservice facilities automatically without one or more drivers of the oneor more vehicles needing to intervene.

Optionally, in the system, the one or more vehicles include globalposition sensing apparatus thereon coupled in communication with thewheel-monitoring apparatus for enabling the one or more vehicles tocommunicate their position to the control centre, so that the controlcentre is operable to identify one or more service facilities mostsuitably geographically disposed to service the one or more vehicles.

According to a eight aspect of the invention, there is provided a methodof operating a system including one or more vehicles, wherein eachvehicle includes a wheel-monitoring apparatus operable to implement amethod pursuant to at least one of the first, second and third aspectsof the present invention, the system comprising:

-   (a) a control centre for coordinating repair or maintenance of the    one or more vehicles;-   (b) one or more service facilities operable to perform repair or    replacement on the one or more vehicles;    wherein the method includes steps of:-   (c) enabling each wheel-monitoring apparatus to monitor operation of    its one or more associated wheels and to detect when a problem or    potential problem arises therewith;-   (d) enabling each wheel-monitoring apparatus to communicate the    problem or potential problem to the control centre, for the control    centre to identify one or more service facilities capable of    addressing the problem or potential problem; and-   (e) enabling the control centre to communicate instructions to the    one or more vehicles whose wheel-monitoring apparatus has detected a    problem or potential problem to the identified one or more service    facilities for the problem or potential problem to be addressed.

According to an ninth aspect of the invention, there is provided asoftware product recorded on a data carrier, the product beingexecutable on computing hardware for executing a method pursuant to atleast one of the first, second and third aspects of the presentinvention.

Features of the invention are susceptible to being combined together inany combination without departing from the scope of the invention asdefined by the appended claims.

DESCRIPTION OF THE DIAGRAMS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the following diagrams wherein:

FIG. 1 is an illustration of a wheel of a contemporary heavy commercialvehicle;

FIG. 2 is a schematic cross-sectional view of a portion of the wheel ofFIG. 1;

FIG. 3 is a schematic cross-sectional view of a tyre (tire) of the wheelof FIG. 1;

FIG. 4 is a cross-sectional view of a contemporary front wheel assemblyof a heavy commercial vehicle;

FIG. 5 is a cross-sectional view of a contemporary rear wheel assemblyof a heavy commercial vehicle;

FIG. 6 is a schematic cross-sectional view of the wheel of FIG. 1illustrating potential locations for mounting monitoring modules for usepursuant to the present invention; the potential locations includehub-mounting at a location L1, hub rim-mounting at a location L2, andin-tyre mounting at a sidewall location L3 and a im location L4;

FIG. 7 is a schematic cross-sectional view of a tyre of the wheel ofFIG. 1 with its monitoring module mounted at a location L2 on a rim of ahub of the wheel with a wire connection from the module to a patchantenna exposed on the hub;

FIG. 8 is a schematic cross-sectional view of a tyre of the wheel ofFIG. 1 with its monitoring module mounted at a location L3 on the tyre,the module being provided with a film antenna wrapped around an edge ofthe tyre and exposed on an exterior surface of the tyre;

FIG. 9 is a schematic diagram illustrating spatial movement of amonitoring module mounted on the wheel of FIG. 1, together with arepresentation of a spring suspension together with a representation offorces acting upon the wheel when in operation;

FIG. 10 is an graph illustrating a general form of acceleration signalobtainable in operation from the monitoring module mounted at thelocation L3 as shown in FIG. 6;

FIG. 11 is a first implementation of a wheel- and tyre-monitoringapparatus for use pursuant to the present invention with the wheel ofFIG. 1, the monitoring apparatus being operable to process accelerationsignals;

FIG. 12 is a second implementation of a wheel- and tyre-monitoringapparatus for use pursuant to the present invention with the wheel ofFIG. 1; the monitoring apparatus being operable to process pressuresignals;

FIG. 13 is a third implementation of a wheel- and tyre-monitoringapparatus for use pursuant to the present invention for use with thewheel of FIG. 1, the monitoring apparatus being operable to process bothacceleration and pressure signals;

FIG. 14 is a schematic diagram of a monitoring module operable to bemounted onto the wheel of FIG. 1 and to sense operation characteristicsof the wheel;

FIGS. 15 a to 15 e illustrate various alternative network communicationtopographies for monitoring modules mounted at various location on thewheel of FIGS. 1 and 6;

FIG. 16 is a schematic illustration of a wheel monitoring system for usepursuant to the present invention for a heavy commercial vehicle inconjunction with a remote control facility and service facility;

FIGS. 17 a to 17 e are an illustration of a method pursuant to thepresent invention for locating positions of one or more modules of thesystem of FIG. 16;

FIGS. 18 a to 18 e are illustrations of an alternative method pursuantto the present invention for locating positions of one or more modulesof the system of FIG. 16;

FIG. 19 is an illustration of a business system associated with anenterprise operating a fleet of heavy commercial vehicles in relation toservice centres and depots;

FIG. 20 is an illustration of the wheel of FIG. 1 provided with a moduleincluding an accelerometer, the module and its accelerometer beingmounted such that its sensing axes are angularly misaligned with truetraverse, radial and tangential axes of the wheel; and

FIG. 21 is a fourth implementation of a wheel- and tyre-monitoringapparatus for use when implementing the present invention for use withthe wheel of FIG. 20, the monitoring apparatus being operable to processacceleration signals.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

1. Context of the Present Invention

Commercial enterprises which operate fleets of vehicles, for examplefleets of heavy commercial vehicles, face different problems withvehicle maintenance and safety in comparison to private automobileowners for which simple contemporary tyre monitoring devices havealready been developed as elucidated in the foregoing. Reliability andsafety for an enterprise operating a fleet of vehicles is extremelyimportant on account of one accident, breakdown or legal incidentpotentially adversely affecting the enterprise's reputation andrelationship with its customers. Vehicle maintenance, and avoidance ofvehicle technical problems before they arise and cause disruption, is ofconsiderable importance to enterprises operating fleets of vehicles.

In a fleet of vehicles, for example heavy commercial vehicles, there aremultiple vehicles, and a set of wheel hubs for the vehicles which areequipped with new tyres at various times. Wheel hubs can potentially beswapped between vehicles and be sporadically furnished with new tyreswhen their existing tyres are deemed to have been worn out. Moreover, incertain climates, for example Northern Europe and Canada, there is alegal requirement to switch between winter tyres and summer tyres; suchswitch between winter tyres and summer tyres is achieved by exchangingwheel hubs rather than removing tyres from their respective hubs. Wheelsare therefore customarily placed in storage when not in use on vehicles.When the wheels and their associated tyres are in storage, various abuseevents can potentially arise which can adverse effect vehicle safetywhen the wheels and their tyres are reinstalled onto vehicles again.Such abuse events include tampering events for example.

Enterprises operating fleets of vehicles normally achieve greatestcommercial efficiency when their vehicles are virtually all in useearning revenue; vehicles undergoing repair or standing idle representan investment which does not generate profit, and can even represent adepreciation in value. An issue associated therewith is efficientmaintenance of vehicles which are intensively in use, especially withregard to their wheels and tyres. The present invention is of benefit byenabling improved identification of wheels modules for monitoring andpredicting potential problems with wheels and tyres; fleet vehicles can,for example, be recalled or rescheduled for maintenance purposes.Increased quality of monitoring is achieved by using more optimal andinnovative sensor configurations and associated data processing. Suchimproved monitoring is achieved by employing complex configurations ofwheel monitors which themselves represent a complex management and datagathering problem.

Referring to FIG. 1, there is shown in side view a schematic diagram ofa wheel of a heavy commercial vehicle. The wheel is indicated generallyby 10. Moreover, the wheel 10 comprises a steel hub indicted by 20 and atyre (tire) denoted by 30. The tyre 30 is contemporarily often tubeless,namely does not include any separate inner tube. A circular inner flange40 of the hub 20 includes a circular arrangement of mounting holes 50for receiving bolts or similar fasteners for attaching the wheel 10 toan axle (not shown in FIG. 1) of its associated vehicle. Extendingradially outwards from the inner flange 40 is a substantiallyfrusto-conical web 60 having a radial series of circular or ellipticalventilation holes 70 formed therein as illustrated, for example one ofthese ventilation holes 70 enables access to an air valve 80 in fluid(air) communication with a volume enclosed by the tyre 30 for purposesof inflating or deflating the tyre 30. At its perimeter, thefrusto-conical web 60 is coupled to a circular rim 90. The circular rim90 is operative to receive the tyre 30.

In FIG. 1, a cross-sectional axis is denoted by A-A and a correspondingcross-sectional view of the wheel 10 is shown in FIG. 2 forsubstantially an upper portion of the wheel 10. The wheel 10 has ageneral form which has evolved over many years to substantially anoptimal implementation for reasons which will now be elucidated. Theinner flange 40 is provided with its regularly spaced configuration ofmounting holes 50 for mounting securely the wheel 10 usingaforementioned bolts or fasteners to an end of a wheel axle 110 of thecorresponding vehicle; the wheel axle 110 is operable to rotate about anaxis B-B. An excess of holes 50 is often provided to be more certain ofretaining the wheel 10 onto the wheel axle 110. Usually, for heavycommercial vehicles, a disc brake 115 is included near an end of thewheel axle 110 in relative close proximity to the frusto-conical web 60and its associated ventilation holes 70. Moreover, an ABS angular sensorencoder 118 for implementing an ABS baking system for sensing an angularorientation of the axle 110 and hence that of the wheel 10 iscontemporarily included as standard components on heavy commercialvehicles; the angular sensor encoder 118 is operable to generate asignal indicative of an angular orientation θ of the wheel 10. Theangular sensor encoder 118 is often implemented as an optical,electrostatic and/or magnetic sensing device.

In operation, when bringing a commercial vehicle weighing 10 tonnes froma speed of 80 km/hour to standstill within a few seconds corresponds toabsorbing kinetic energy in an order of 3×10⁶ Joules which can result inan instantaneous rate of energy dissipation in the disc brake 115associated with the axle 110 in an order of ten's of kilowatts. Theholes 70 in the frusto-conical web 60 thus enable air circulation toreach one or more metal discs of the disc brake 115 for coolingpurposes. Moreover, the holes 70 in the web 60 also assist to reduce anunsprung weight of the wheel 10 without adversely influencing itsmechanical strength, as well as providing access for the valve 80. Therim 90 has various ridges formed therein to enhance its mechanicalstrength and also has end ridges 170 to provide reliable retention ofthe tyre 30 in operation. The tyre 30 encloses a volume denoted by 120which is maintained at an elevated pressure P during operation.

Referring next to FIG. 3, an illustrative cross-sectional view of aportion of the tyre 30 is shown. The tyre 30 includes inner edges 180for abutment onto the ridges 170 of the circular rim 90. The inner edges180 are often reinforced using steel rings or bands 200 molded into thetyre 30. Moreover, the tyre 30 includes one or more reinforced wovenmetal and/or reinforced fibre meshes 210 embedded by molding into thetyre 30. A tread portion 220 of the tyre 30 has a greater radialthickness in comparison to a lateral thickness of side walls 230 of thetyre 30; the tread portion 220 is thicker for accommodating treads ofthe tyre 30. In operation, the tread portion 220 is operable to providea firm grip to a road surface (not shown) as well as a water drainingfunction, whereas the walls 230 are designed to periodically elasticallyflex when the wheel 10 with its associated tyre 30 rotate in operationon the road surface.

There are several potential modes of failure of the tyre 30, and even ofthe wheel 10, which an enterprise operating a fleet of vehicles, forexample heavy commercial vehicles, employing such wheels 10 would desireto identify and correct before various modes of failure cause breakdown,accident or delay involving vehicles. Problems that are encounteredinclude:

-   (a) the air pressure P in the tyre 30 is too low causing excessive    flexure of the walls 230 and associated one or more meshes 210 with    a risk of them work-hardening and prematurely fracturing; when the    air pressure P is too low, there arises an excessive contact area    between the tyre 30 and a road surface interfacing to the tyre 30    causing excessive tyre wear, and also increased rolling resistance    and hence poor vehicle fuel economy; too much contact area between    the tyre 30 and the road surface can also paradoxically result in    inferior grip between the tyre 30 and the road surface in icy and    snowy conditions because contact force between the tyre 30 and the    road surface is not as concentrated as ideally desired to force the    tyre 30 to conform to surface irregularities in the road surface    susceptible to providing grip. Excess deformation of the tyre 30    when its internal air pressure P is too low potentially causes    excess energy dissipation by a degree of non-elastic deformation    within the tyre 30 with associated temperature rise resulting    therefrom which can, in a worst case, exceed a temperature which    material from which the tyre 30 is fabricated is able to tolerate.    Moreover, when the pressure P within the tyre 30 is too low, there    is also a risk that the inner edges 180 loose their seal with the    ridges 170 when subject to severe lateral stress, for example when    scuffing along a curb stone, with subsequent sudden loss of air from    the tyre 30;-   (b) one or more of bolts or fasteners applied to the holes 50 for    securing the wheel 10 to the wheel axle 110 can potentially be    inadequately tightened during attachment of the wheel 10 to the axle    110, or are susceptible to potentially working loose in operation;    such loosening and potential loss of one or more of the bolts or    fasteners can result in the wheel 10 wobbling or rattling on the    axle 110 and, in a worst case, even becoming detached from the axle    110 and rolling off (!);-   (c) the tyre 30 and/or the valve 80 can develop a leak such that a    partial loss of the pressure P within the tyre 30 in operation    arises; if such loss of pressure P is undetected, problems as    outlined in (a) in the foregoing can potentially arise; however, the    pressure P is a function of a temperature of the tyre T_(tyre), and    also whether or not the tyre 30 is periodically maintained by being    recharged with compressed air or other gas through its valve 80;-   (d) the tyre 30 can develop in use an imbalance, for example a    portion of rubber of the tyre 30 can become unevenly eroded with    use, or a balancing weight earlier added to the wheel 10 can become    detached from the wheel 10; in a situation of a double-tyre    arrangement as illustrated in FIG. 5 often employed at a rear of a    heavy commercial vehicle, it is known for a building brick or    similar object to occasionally become wedged between the    double-tyres and represent a dangerous projectile in an event of the    object subsequently becoming dislodged by centrifugal force whilst    the double wheel is rotating; such ejected objects from tyres    potentially represents a considerable danger when they smash through    an automobile front window resulting in injury or accident; and-   (e) the tyre 30 can become oval or distorted in some other    symmetrical manner which does not necessarily cause an asymmetrical    imbalance to the wheel 10; moreover, the hub 20 itself can become    bent and thereby skewed out-of-plane without necessarily causing an    asymmetrical imbalance in the wheel 10.

Referring to FIGS. 4 and 5, there are shown diagrams of examplecontemporary manufactured front and rear wheel assemblies of a heavycommercial vehicle to illustrate how compact regions around vehiclewheels are in practice. There is little extra volume in the front andwheel assemblies for accommodating additional instrumentation formonitoring wheel operating conditions. Amongst other factors, componentsassociated with the aforesaid brake 115 are included in close proximityto the wheel 10 in operation; the brake 115 has associated therewithother components such as servo actuators for forcing brake padcomponents against a disk component of the brake 115. However, it isconventional practice to include around the wheel axle 110 and in closeproximity to the wheel 10 the aforesaid ABS sensor encoder 118 (notshown in FIGS. 4 and 5) for measuring the angular position θ of thewheel 10 when mounted on its axle 110.

Characteristics which are beneficial to measure in order to monitorwheel 10 and associated tyre 30 condition include temperature T,pressure P and instantaneous acceleration A during operation. It isadditionally also feasible to include film strain gauges within orbonded onto walls 230 of the tyre 30 to measure their wall flexure.Temperature T and acceleration A can be measured at various spatialpositions on the wheel 10 with mutually different results, whereas thepressure P developed within the volume denoted by 120 enclosed by thetyre 30 in operation is effectively similar because the pressure Pequalizes in a relatively short period of time; pressure equalization isestimated to occur within a few milliseconds on account of pressurepulses being able to propagate at a velocity in an order of 250meters/second within the volume 120. The wheel 10 has a diameter in theorder of 1 meter.

FIG. 6 illustrates schematically categories of locations whereat sensorsare beneficially mounted to the wheel 10. When several sensors areincluded at each category of location, the several sensors arebeneficially distributed at positions angularly distributed around thewheel 10 for providing most representative information indicative ofoperation of the hub 20 and its tyre 30.

At a location L1, fasteners are beneficially employed to attach a firstsensor module to the hub 20 or even via one or more of the holes 50 tothe axle 110. The first sensor module is capable of monitoring the tyrepressure P by way of fluid (air or gas) communication to the valve 80,is capable of monitoring a temperature T_(hub) of the hub 20 and iscapable of sensing accelerations A in one-, two- or three-orthogonalaxes (x, y, z) at the hub 20 depending upon type of accelerometeremployed. Beneficially, one or more of a pressure sensor and anaccelerometer included in the first sensor module for performingmeasurements are silicon micromachined integrated electronic componentscontemporarily known as MEMS (“Micro-Electronic Mechanical Systems”).The temperature T_(hub) of the hub 20 will often be different from thetemperature T_(tyre) of the tyre 30; a temperature T_(mod) measured atthe first module is hence not ideally representative of the tyre 30temperature T_(tyre) and thus condition of the tyre 30; the hub 20 willoften be subject to direct cooling air flows, and during braking eventswill be heated up rapidly by warm air flowing from the associated discbrake 115 which, as elucidated in the foregoing, can be subject tosudden peak dissipations of energy of many kiloWatts, for example duringand shortly after performing emergency braking. The first module at thelocation L1 is not totally screened by conductive components whichrenders short-distance wireless communication possible between the firstmodule and an electronic control unit (ECU) or electronic managementsystem of the vehicle. The first sensor module at the location L1 ismost accessible and susceptible to being retrofitted to vehicles withminimal mechanical changes being required.

A second sensor module is beneficially mounted to an inside surface ofthe rim 90 at a location L2 and thereby is subject directly to thepressure P developed within the tyre 30 in operation. The second moduleat this location L2, when measuring the temperature T_(mod) thereat, iscapable of providing an accurate measurement of the temperature T_(tyre)of the tyre 30 as well as the aforesaid pressure P. Moreover, one ormore accelerometers included within the second module for measuring theacceleration A at the location L2 are at a greater radial distance fromthe axis B-B (see FIG. 2) than the first module at the location L1, andare therefore subject to greater radial components of accelerationresulting from rotation of the wheel 10. A disadvantage of mounting thesecond sensor module at the position L2 is that the mesh 210 incombination with the rim 90 have a tendency to form a Faraday cage whichseverely attenuates wireless transmissions from the second module,unless the second module has an antenna exit through the rim 90, forexample a small air-tight hole through which an antenna wire coupled tothe second module at the position L2 is extended out onto thefrusto-conical web 60 for enhancing wireless communication efficiency.In FIG. 7, there is shown an example wherein the second module at thelocation L2 is coupled via an antenna wire 300 through an insulatedfeed-through 310, installed in the rim 90 and operable to withstand thepressure P, to a film metal patch antenna 320; optionally, the patchantenna 320 is affixed to the frusto-conical web 60 for mechanicalprotection. Alternatively, or additionally, the second module at thelocation L2 is electrically coupled to the mesh 210 of the tyre 30 andis operable to employ this mesh 210 as an antenna for communicating bywireless to the aforesaid electronic control unit (ECU) or an electronicvehicle management system. As a yet further alternative, the secondmodule at the location L2 can be directly electrically coupled by wirethrough the feed-through 310 or by conductive film connection to thefirst module at the location L1 and optionally derive power therefrom aswell as communicating measurement data thereto.

A third sensor module is beneficially mounted on an inside surface ofthe tyre 30 at a location L3, for example by bonding the third moduleonto the tyre 30 using rubber or plastics material bonding agents orsimilar before the tyre 30 is mounted to the hub 20; alternatively, useof snap-type press-fit mounting of the third sensor module to the tyre30 is also feasible and faster to employ when manufacturing andservicing the tyre 30. The third module at the location L3 is capable ofmeasuring the temperature T_(mod) thereat and thereby providing a directrepresentative indication of tyre temperature T_(tyre), a representativedirect indication of the pressure P and is also able to provide anrepresentative indication of flexural characteristics of the walls 230of the tyre 30 by way of acceleration A measurements or strain gaugemeasurements; however, the acceleration signals generated by the thirdmodule at the location L3 are a complex modulation of variousacceleration components as the wheel 10 rotates in operation and itsside walls 230 flex, whereas the accelerometer of the first modulemounted at the location L1 is operable to generate acceleration signalswhich include a relatively greater magnitude of linear accelerationcomponents therein which renders the first module at the location L1potentially better suited for monitoring such linear accelerationcomponents. Optionally, the third module at the location L3 is alsocoupled to one or more resistive-film or fibre-optical strain gaugesensors (not shown) coupled onto or even embedded within the rubbermaterial of the tyre 30, for example onto the side wall 230 and/orperipheral rim of the tyre 30. The third module mounted at the locationL3 suffers a similar wireless communication problem to the second moduleat the location L2 in that the mesh 210 in combination with the rim 90functions as a Faraday cage to attenuate wireless communication from thevolume 120 within the tyre 30. In order to improve wirelesscommunication, the third module at the location L3 is optionallyprovided with a thin-film conductive antenna 350, for example fabricatedby metal film sandwiched between layers of flexible insulating materialsuch as Kapton as illustrated in FIG. 8. The antenna 350 is beneficiallywrapped around the inner edges 180 and up around an outside wall surfaceof the tyre 30. The second module at the location L2 is also susceptibleto being provided with such a thin-film antenna, for example disposedover an edge of the rim 90 and even extending onto the frusto-conicalweb 60. However, such thin-film antennas are susceptible to beingdamaged when the tyre 30 is installed onto the hub 20 unless adequatelyprotected with a rubber protective film 360 or similar component addedto provide mechanical protection. Alternatively, or additionally, thethird module is susceptible to having its antenna coupled electricallyto the mesh 210 of the tyre 30 which is then capable of functioning asan antenna; the third module is beneficially provided with an electricalpiercing pin for penetrating during installation through an inside ofthe side wall 230 for providing an electrical connection to theconductive mesh 210. Yet alternatively, the second module at thelocation L2 can be operable to function as a wireless relay node forconveying signals from the third module at the location L3 via thesecond module at the location L2 to an electronic control unit (ECU) ofthe vehicle; such nodal communication between modules mounted onto thewheel 10 will be elucidated in more detail later and corresponds to themodules cooperating to form a communication network.

A fourth module is optionally mounted at a location L4 adjacent a treadregion of the tyre 30 and functions in a generally similar manner to thethird module mounted at the location L3.

Measurement signals generated by the first, second and third modules atthe locations L1, L2 and L3 respectively will now be further elucidatedwith reference to FIG. 9.

In FIG. 9, there is shown the axis of rotation B-B around which thewheel 10 revolves in operation. The wheel 10 is provided via the axle110 with a leaf spring and/or air pneumatic suspension coupled to achassis CH of the vehicle; the suspension is denoted by a springconstant K_(S). Forces applied to the tyre 30 from a road surface incontact with the tyre 30 are denoted by a force F(t); the tyre 30 has aspring compliance described by a spring constant K_(T) which isdependent on the pressure P within the tyre 30 and also mechanicaldesign of the tyre 30. The first, second and third sensor modules at thelocations L1, L2 and L3 respectively are each denoted by a module 400which circumscribes in operation a radial path denoted by 410 when thewheel 10 rotates around the axis B-B corresponding to the axle 110. Theradial path 410 has a radius r and the module 400 is inclined at aninclination angle φ relative to a normal radial direction 420. Themodule 400 is operable to measure at least one of:

-   (a) a temperature T_(mod) at the module 400;-   (b) the pressure P at the module 400; and-   (c) linear acceleration in one or more axes x, y, z as, for example,    illustrated in FIG. 9, wherein the z-axis is parallel to the axis    B-B when the inclination angle φ is 0 degrees, the y-axis    corresponds to a radial direction for the wheel 10 when the    inclination angle φ is 0 degrees, and the x-axis corresponds to a    tangential direction whose associated acceleration is weakly    affected by the inclination angle φ when near 0 degrees.

When the module 400 is mounted at the location L1, it measures thepressure P of the tyre 30 via its valve 80.

As elucidated in the foregoing, the module 400 is optionally furnishedwith other types of sensors, for example resistive strain gauges,piezo-electric strain gauges, moisture sensors, and so forth if desired.It is convenient, for identification purposes, that the module 400 isoptionally provided with a magnetic sensor, for example implementedusing a magnetic reed-relay switch operable to electrically conduct whena permanent magnet having, for example, a near-field magnetic fieldstrength of 100 milliTesla is placed in near proximity to the module400, for example within a distance of 10 cm therefrom.

With reference to FIG. 9, when the wheel 10 rotates at a constantangular rate ω, and the inclination angle φ is substantially 0 degrees,the acceleration A_(x) measured by the x-axis accelerometer is given byEquation 1 (Eq. 1):A _(x) =g sin(ωt+λ)  Eq. 1wherein

-   A_(x)=an x-axis acceleration measurement;-   r=a radius from the axis B-B at which the module 400 is mounted;-   ω=an angular rotation rate of the wheel 10;-   g=a gravitational constant (circa 10 m/s/s); and-   λ=an angular offset.

When the wheel 10 rotates at the constant angular rate ω, and theinclination angle φ is substantially 0 degrees, the acceleration A_(y)measured by the y-axis accelerometer is given by Equation 2 (Eq. 2):A _(y) =rω ² +g sin(ωt+λ)  Eq. 2wherein

-   A_(y)=a y-axis acceleration measurement;-   r=the radius from the axis B-B at which the module 400 is mounted;-   ω=the angular rotation rate of the wheel 10;-   g=the gravitational constant (circa 10 m/s/s); and-   λ=an angular offset.

Beneficially, the wheel 10 when mounted on its axle 110 is provided withthe aforementioned ABS angular sensor encoder 118 for measuring thepositional angle θ of the wheel 10 and the angular turning rate ω=dθ/dtof the wheel 10. Disparity of the measured acceleration A_(x) fromEquation 1 with measurements from such an ABS sensor encoder 118 issusceptible to being used detect one or more of:

-   (i) detecting malfunction of the ABS sensor encoder 118; and-   (ii) slip of the tyre 30 relative to the hub 20, especially    pertinent when sensing at the location L3 (although this slip only    exceptionally occurs usually with catastrophic results).

Assuming such an ABS encoder sensor 118 is functioning correctly,checking the acceleration A_(x) against change in turning angle θdetermined by the ABS sensor encoder 118 can be, for example, employedto dynamically confirm correct operation of the module 400.

The module 400 is also capable of measuring accelerations A_(y) andA_(x) in substantially y- and z-directions respectively when theinclination angle φ is non-zero which is, for example, pertinent for thethird module at the location L3 when the wall 230 of the tyre 30 flexes,or at the locations L1 and L2 when the hub 20 is loose on its fastenersor skewed in relation to the axle 110. Measured acceleration signals areprovided approximately as defined in Equations 3 and 4 (Eqs. 3 and 4):A _(z)=(rω ² +g sin(ωt+λ))sin φ  Eq. 3A _(y)=(rω ² +g sin(ωt+λ))cos φ  Eq. 4

For the locations L1 and L2, the inclination angle φ for the module 400mounted in an orientation as depicted in FIG. 9 is normallysubstantially zero such that the acceleration A_(z) is normally of arelatively small magnitude and the acceleration A_(y) is a summation offorces arising from the force F(t) resulting from road surfacecharacteristics, centrifugal components rω² arising from turning of thewheel 10 and the force of gravity g modulated by turning of the wheel10. However, in an event of imbalance of the wheel 10 arising from thehub 20 becoming skewed, for example:

-   (a) due to loosening of the fasteners or bolts used to attach the    hub 20 via its holes 50 to the axle 110;-   (b) due to the hub 20 becoming deformed due to impact or accident or    fracture, or-   (c) the axle itself 110 being out of alignment due to fault or    impact,    the inclination angle φ becomes a function of an angle of rotation θ    of the wheel 10 as defined by Equation 4 (Eq. 5):    φ=φ_(max) sin(ωt+μ)  Eq. 5    wherein-   φ_(max)=a misalignment angle; and-   μ=angular offset regarding rotation of the wheel 10,    such that Equations 3 to 5 are then susceptible to being used in    combination for determining a nature of the measured accelerations    A_(y) and A_(z) from the module 400 mounted at the locations L1 and    L2. The acceleration signal A_(z) is thus useful, pursuant to the    present invention, for identifying angular misalignment or fastener    problems by monitoring using modules 400 at one or more of the    locations L1 and L2. However, the module 400 mounted at the location    L3 is subject to considerable flexure of the wall 230 which tends to    dominate in magnitude with regard to angular change over angular    misalignment of the axle 110 or lateral wobbling of the wheel 10.    Moreover, as elucidated in the foregoing, mounting the module 400 at    the location L1 is beneficial for measuring the pressure P of the    tyre 30 from its valve 80, but the temperature T_(mod) measured by    the module 400 at the location L1 is not an accurate representation    of temperature T_(tyre) of the tyre 30 on account of intermittent    heating of the brakes 115 in operation. Furthermore, mounting the    module 400 at the location L2 is beneficial for measuring the    pressure P of the tyre 30, as well as measuring a representative    operating temperature of the tyre 30 (namely T_(mod)=T_(tyre) at the    location L2).

When the module 400 is mounted at the location L3, it is capable ofproviding a representative measurement of the pressure P and thetemperature of the tyre 30 (namely T_(mod)=T_(tyre)). However, periodicflexure of the wall 230 of the tyre 30 when the module 400 is mounted atthe location L3 results in the inclination angle φ being a strongfunction of the angle of rotation θ of the wheel 30; the inclinationangle φ then becomes substantially, to a first approximation, theflexural angle of the wall 230 of the tyre 30. For the module 400mounted at the location L3, the inclination angle φ then becomes aseries function as defined in Equation 6 (Eq. 6):

$\begin{matrix}{\phi = {\phi_{0} + {G(P)} + {{H(P)}{\sum\limits_{i = 1}^{n}\;( {k_{i}{\sin( {i( {{\omega\; t} + ɛ_{i}} )} )}} )}}}} & {{Eq}.\mspace{14mu} 6}\end{matrix}$wherein

-   φ₀=angular offset;-   G(P)=a function describing a change in angle of the wall 230 of the    tyre 30 as a function of changes in the pressure P therein for a    portion of the tyre 30 not in contact with a road surface;-   H(P)=a function dependent on the pressure P describing an angular    deflection of the wall 230 when its portion of tyre 30 comes in    contact with the road surface;-   k=a harmonic coefficient;-   i=a harmonic index number;-   ω=the angular rate of rotation of the wheel 10; and-   ε_(i)=an angular offset.

FIG. 10 provides in a signal V1 a qualitative illustration of the angleφ when the module 400 is mounted at the location L3 and the wheel 10 isrotating; the inclination angle φ changes rapidly with flexure of thetyre wall 230 when a portion of the tyre 30 carrying the module 400 onits inside wall 230 comes into contact with a road surface. An abscissaaxis in FIG. 10 represents the rotation angle θ with time t, namelyangle θ=ωt; an ordinate axis in FIG. 10 represents substantially thewall inclination angle φ. A period 500 corresponds to one completerevolution of the wheel 10, namely Δθ=2π.

Apparatus for use with the present invention is, for example, capable ofbeing employed in a first analysis method including steps of computingexpected performance characteristics of the tyre 30 and then comparingthe expected performance characteristics against measuredcharacteristics. The first method includes steps as follows:

-   (a) for a given type of tyre 30 defining the angle φ₀ and the    functions G and H in Equation 5, for a given pressure P measured for    the tyre 30, for a given temperature T_(tyre) measured at the tyre    30, and for a given angular rotation rate w of the tyre 30    determined for example from the aforesaid ABS encoder sensor 118,    computing a corresponding expected simulated angle φ, and deriving    therefrom a simulated magnitude of the acceleration A_(z) as would    be expected to be generated from the accelerometer included in the    module 400 mounted at the location L3;-   (b) sensing representative samples of the acceleration A_(z) as    measured by the module 400; and-   (c) checking to determine whether or not the simulated and measured    accelerations A_(z) mutually differ by more than a predefined    threshold amount; if they do not mutually substantially correspond,    there is inferred therefrom that the tyre 30 is potentially    defective and needs to be replaced.

For example, it is potentially possible to identify degradation of themesh 210 before failure of the tyre 30 occurs in operation. Suchsimulation beneficially requires harmonic synthesis to be executed oncomputing hardware included within the module 400 and/or in anelectronic control unit (ECU) of the vehicle to derive the simulatedacceleration A_(z).

Apparatus for use with the present invention is, for example, capable ofbeing employed in a second analysis method including steps of samplingdata representative of the acceleration A_(z) occurring in operation atthe tyre 30, subjecting the sampled data to harmonic analysis, forexample by applying Fast Fourier Transform (FFT) or similar type oftransform, then deriving parameters from the harmonic analysis, and thencomparing the computed parameters with those that are expected for thetyre 30; if there is a mutual difference between the computed andexpected parameters for the tyre 30 by more than a predefined thresholdamount, potential failure of the tyre 30 can be detected and the tyre 30replaced if necessary. The second method includes steps as follows areexecuted:

-   (a) sampling signals generated by the accelerometer in the module    400 representative of the acceleration A_(z) to provide    corresponding sampled data, and then subjecting the sampled data to    harmonic analysis, for example by way of an efficient Fast Fourier    Transform (FFT) algorithm, to derive its harmonic content and hence    a series of harmonic coefficients; optionally phase relationships    between the harmonics, as denoted by ε_(i) in Equation 6 (Eq. 6),    are also computed for use when making a comparison;-   (b) from the harmonic analysis, in combination with a knowledge of    temperature T_(tyre) and pressure P of the tyre 30, determining a    type of tyre 30 present on the wheel 10, based upon a look-up    reference list of tyre characteristics such as suppleness and    elasticity as well as tyre wall shape and profile; and-   (c) comparing the determined type of tyre 30 with the actual    identification of type for the tyre 30; if there is mutual variance    therebetween by more than a predefine threshold amount, the tyre 30    is determined to be potentially faulty and potentially in need of    being replaced.

When utilizing the aforesaid second method, in an event of the predictedtyre and the actual tyre 30 on the wheel 10 being mutually at variance,degradation or fault in the tyre 30 can thereby be inferred therefrom.As will be elucidated later, it is beneficial that the module 400 whenmounted on the wall 230 of the tyre 30 as depicted in FIG. 8 be providedwith a distinguishing identification code (ID). The code is beneficiallyindicative of the characteristics of the tyre 30 to which the module 400is attached at the position L3. The module 400 is operable tocommunicate the identification code (ID) by wireless to an electroniccontrol unit (ECU) which is operable to execute the variance comparison.Beneficially, harmonic analysis is also applied to one of more of theacceleration signals A_(x) and A_(y) for further confirming reliabilityof the harmonic analysis executed pursuant to this second method.

Whereas the module 400 mounted at the location L3 is especiallyeffective for detecting potential problems or defects arising in respectof flexure and dissipation within the tyre 30, the module 400 mounted atthe location L1 is especially effective for measuring variations inasymmetry in the wheel 10, and also for determining a type of asymmetryin the wheel 10 and its associated tyre 30. Even more preferably fordetecting imbalance and also type of imbalance in the wheel 10, themodule 400 is mounted in a non-rotating manner onto the shaft 110substantially corresponding to the axis B-B. However, more wheeldiagnostic information regarding imbalance in the wheel 10 issusceptible to being derived when the module 400 is mounted onto thewheel 10 and operable to rotated with the wheel 10, preferably near itsaxis B-B of rotation, for example substantially at the location L1. Aswill be elucidated in more detail later, monitoring the pressure P asthe wheel 10 rotates provides unexpectedly considerable additionalinformation regarding performance of the tyre 30, for examplemulti-lobed distortions of the tyre 30.

Examples of a wheel monitoring apparatus, generally denoted by 1, isshown in FIGS. 11, 12 13 and 21. The wheel monitoring apparatus 1 mayinclude any one of the data processing apparatuses 600,680,690 and 2200shown in FIGS. 11, 12, 13, and 21.

Referring to FIG. 11, there is shown a data processing apparatuspursuant to the present invention indicated generally by 600; the dataprocessing arrangement is operable to provide wheel- andtyre-monitoring. The data processing apparatus 600 is capable of beingimplemented in at least one of the module 400 and the aforesaidelectronic control unit (ECU), depending upon where the processing issusceptible to being most conveniently and efficiently executed.Moreover, the processing arrangement 600 is susceptible to beingimplemented in at least one of hardware, and software executable inoperation on computing hardware. The software is beneficially providedas a software product executable on the computing hardware. The softwareproduct is beneficially conveyed to the apparatus 600 on a data carrier;the data carrier is beneficially at least one of: a solid-stateelectronic data carrier, a wireless signal, an electrical signal, anoptical-fibre signal, an optically and/or magnetically readable datacarrier.

Under steady-state rotation of the wheel 10, namely with constantangular velocity ω, temporal variations in the radial accelerationA_(y), namely dAy/dt, are of substantially zero magnitude for theinclination angle φ being substantially zero, other than effects due togravity g which are correlated with the rotation angle θ of the wheel10. Momentary acceleration generated from a road surface onto which thetyre 30 contacts in operation results in the force F(t) as shown in FIG.9 varying with time t and giving rise to varying components in a linearvertically-directed acceleration A_(v) experienced at the axle 110 whichare not correlated with periodic rotation of the wheel 10. However,components in the linear vertically-directed acceleration A_(v) whichcorrelate with rotation of the wheel 10, for example as referenced byway of the aforesaid ABS encoder sensor 118 providing an indication ofthe rotation angle θ of the wheel 10 and its angular frequency ofrotation ω, are of benefit for determining imbalance in the wheel 10,and also potentially elucidating a type of imbalance present in thewheel 10. The ABS encoder sensor and its associated signal processingcircuits are denoted by 118 in FIG. 11. When one or more of the modules400 are mounted onto the wheel 10 at one or more of the locations L1 toL4, they rotate in operation together with the wheel 10. In consequence,the one or more accelerometers in the one or more modules 400 measuringthe accelerations A_(x) and A_(y) as depicted in FIG. 9 are allsensitive to linear vertically-directed acceleration in response torotation of the wheel 10. In order to suitably condition theaccelerations A_(x) and A_(y), it is necessary for the one or moremodules 400 and/or an electronic control unit (ECU) in wirelesscommunication therewith to perform angular resolving, for example asdescribed in Equation 7 (Eq. 7):A _(v) =d ₁ sin(ωt)·A _(x) +d ₂ cos(ωt)·A _(y)  Eq. 7whereind₁, d₂=scaling constants.

Such angular resolution is executed in operation in a resolver denotedby 620 in FIG. 11. The resolver 620 beneficially receives its angularreference for the rotation angle θ from the ABS encoder sensor and itsassociated circuits 118. The resolver 620 is also beneficial in beingoperable to remove an angular dependent component in the accelerationA_(v) due to gravity g which becomes constant in the resolvedacceleration A_(v). Removal of the acceleration component due to gravityg in the resolved acceleration A_(v) is beneficial for auto-scaling theconstants d₁ and d₂ in Equation 7 (Eq. 7) for a condition that the wheel10 is known to be correctly in balance, for example during a calibrationroutine performed after the wheel 10 is newly installed on the vehicle.

By performing harmonic analysis on the signal representing theacceleration A_(v) in respect of the angular frequency of rotation w ofthe wheel 10, for example in a harmonic analyzer denoted by 630 in FIG.11, the severity of the imbalance can be determined; for example, theamplitude of harmonics Q(m) wherein m is a harmonic number in theacceleration A_(v) signal are beneficially individually scaled by aharmonic scaling function y(m) in a scaler 640 and then summed in asumming unit 650 to compute an aggregate S_(tot) summed value. Theaggregate value S_(tot) is then compared in a threshold detector denotedby 660 against a predefined threshold value Th to determine whether ornot the wheel 10 needs attention to correct the imbalance, for exampleby adding balancing weights or exchanging the tyre 30. Equations 8 and 9describe associated computing required:

$\begin{matrix}{S_{tot} = {\sum\limits_{m = 1}^{l}{{Q(m)} \cdot {y(m)}}}} & {{Eq}.\mspace{14mu} 8}\end{matrix}$If S_(tot)

Th, then the wheel 10 needs attention  Eq. 9

Equation 9 corresponds to a decision point DK1 illustrated in FIG. 11.

Optionally, the harmonic scaling function y(m) implemented in the scaler640 is made dependent upon a type of tyre 30 installed on the wheel 10;for example, a robust knobbly tyre installed on the wheel 10 ispotentially able to exhibit a greater degree of imbalance beforerepresenting any form of potential risk than a lean high-performancehigh-speed tyre optimized for reduced energy consumption during driving.Moreover, the harmonic scaling function y(m) implemented in the scaler640 is beneficially also made a function of time t, namely y(m, t) inEquation 8, from an initial time t₀ at which the tyre 30 was installedonto the hub 20. Furthermore, the harmonic scaling function y(m) is alsobeneficially made a function of the number of revolutions as determinedfrom the ABS sensor encoder 118 that the wheel 10 has experienced sincethe tyre 30 was installed thereon, namely y(m, N) where N is the numberof revolutions of the tyre 30. A reason for rendering the harmonicscaling function y(m, t) or y(m, N) variable is that imbalance in awell-worn tyre 30 is more likely to potentially result in tyre 30failure in comparison to a newly-installed substantially unworn tyre 30whose internal mesh 210 has not been subjected to substantialwork-hardening due to repetitive flexure.

The type of imbalance for the wheel 10 as determined from the amplitudeof the harmonics Q(m) is determined from the relative amplitude of givenharmonics; such determination is performed by harmonic analysis in ananalyzer denoted by 670 in FIG. 11. Moreover, such harmonic analysis isbeneficially implemented using a set of software rules, by applying aharmonic stencil to the harmonics to identify a signature of a specifictype of imbalance present, or by feeding data indicative of theamplitude of the harmonic Q(m) into a neural network trained torecognize occurrence of certain types of defects. One or more of thesoftware rules, the harmonic stencil and the neural network arebeneficially optionally rendered dependent upon a type of tyre 30installed onto the hub 20. Moreover, one or more of the rules, theharmonic stencil and the neural network are also beneficially optionallydependent upon an age and/or a degree of wear of the tyre 30. Whencomputing relative amplitude of harmonics Q(m) present in theacceleration A_(v), normalization of the amplitude of the harmonics Q(m)is beneficially implemented as a part of signal processing employed asdepicted in FIG. 11.

For example, when fasteners in the aforementioned holes 50 attaching thehub 20 to the axle 110 have been inadequately tightened or work loosesuch that the hub 20 rattles around on its axle 110, the suspension ofthe vehicle, for example as denoted by the spring K_(s) in FIG. 9, isoften so effective that the driver of the vehicle is unaware of therebeing any problem. The hub 20 slopping around on its bolts or fastenersgives rise to sudden small jolts of the wheel 10 as the wheel 10rotates; it has even been known for the frusto-conical web 60 togenerate a bell-like ringing tone as it is pulse excited into resonancecorresponding to a “cos 2θ mode” of flexure, namely hoop-likedeformation of the rim 90 and the frusto-conical web 60. These smallsudden jolts give rise to signal energy in relatively high harmonics,for example in a range of 10^(th) to 20^(th) harmonic in the harmonicsQ(m), which the scaling function y(m) can be arranged to isolate forspecifically detecting that the wheel 10 is loose on its fasteners forwarning the driver of the vehicle.

Beneficially, several different scaling functions y(m) are appliedconcurrently to the harmonics Q(m) so that occurrences of severaldifferent types of imbalance are monitored simultaneously by the dataprocessing apparatus 600.

In an alternative, or additional, implementation of the data processingapparatus 600, the pressure P measured by the module 400 is provided tothe harmonic analyzer 630 instead of the resolved acceleration A_(v) ina manner as depicted in FIG. 12; in FIG. 12, the data processingapparatus 600 adapted to harmonically analyze the pressure P isindicated generally by 680. Irregularities in the tyre 30, for examplelocal bulges or weaknesses causing blisters in the tyre 30, are manifestas pressure pulses at certain angular 9 positions as the wheel 10rotates in operation. By analyzing variations in the pressure P as afunction of rotation angle θ of the wheel 10, namely components of thepressure P correlated with turning rate ω, it is feasible to provideadditional monitoring of the tyre 30 for improving detection of defects,or potential defects, in the tyre 30. The data processing apparatus 680functions in a generally similar manner to the data processing apparatus600 except that the pressure P is analyzed instead of the accelerationA_(v). Optionally, a data processing apparatus pursuant to the presentinvention is provided by combining together the data processingapparatus 600, 680 so as to provide for concurrent or periodicallyalternating harmonic analysis and monitoring of the acceleration A_(v)and the pressure P as depicted in FIG. 13 and as indicated by 690therein; there is provided a switching arrangement 695 in the dataprocessing apparatus 690, either implemented in software or hardware,for selecting between the pressure P and the acceleration A_(v). Anadvantage of the data processing apparatus 690 illustrated schematicallyin FIG. 13 is that more comprehensive monitoring to the wheel 10 issusceptible to being achieved in operation.

Aforementioned analysis of flexure of the wall 230 of the tyre 30 assensed by the module 400 mounted at the location L3 is beneficiallycompared in the electronic control unit (ECU) and/or within the module400 with results from harmonic signal analysis performed in respect ofone or more modules 400 positioned at one or more of the locations L1and L2. In an event that the comparison is such that the modules 400located at mutually different locations L1 to L3 give rise to mutuallyconflicting analysis results, there is a high likelihood of potentialproblems with the wheel 10 and/or its tyre 30; a warning message isbeneficially then transmitted from the data processing apparatus 600,680 or 690 as appropriate to a driver of the vehicle and/or to a controlcentre of the enterprise operating a fleet of such vehicles that thereis a need to perform maintenance on the vehicle, for example fordevising logistics for a future maintenance schedule for the vehicle.Such logistics can include, for example, prearranging a replacementwheel to be available and informing a service facility regarding a timeof arrival of the vehicle for maintenance purposes so that appropriatetask scheduling at the service facility can be implemented.

One or more of the modules 400 mounted at one or more of the locationsL1 to L3 are susceptible to being used, optionally in communication withan electronic control unit (ECU), to detect more gradual temporalchanges in the tyre 30, for example a gradual reduction in pressure Pdue to a slow leak therefrom, for example over a period of several weeksor months. Moreover, the one or more modules 400, optionally incooperation with the aforesaid electronic control unit (ECU) in wirelesscommunication with the one or more modules 400, can be used to monitorsudden depressurization of the tyre 30, for example suddendepressurization and subsequent re-pressurization associated withinstalling a new replacement tyre 30 onto the hub 20. Monitoring of suchsudden depressurization is important when an earlier tyre 30 equippedwith a module 400 mounted therein is exchanged for a replacement tyre 30devoid of any such module 400, so that parameters for various signalprocessing functions as depicted, for example, in FIG. 11 can beappropriately selected by the apparatus 600, 680 or 690. When theidentity and condition of the tyre 30 is not reliably known, there arebeneficially adopted in the data processing apparatus 600, 680 or 690default values for parameters indicative of a tyre 30 with asubstantially medium degree of tread wear. Beneficially, there is issueda message “not reliable information” or similar in an event of suchsudden depressurization having been detected to alert the driver thatthe electronic control unit (ECU) is being supplied with potentiallynon-representative information. Such a situation can arise whenunauthorised swapping of the tyre 30 has occurred or tampering with thetyre 30 has occurred for example.

The module 400 will now be described in overview with reference to FIG.14. In operation, the module 400 is required to be robust and alsoinexpensive in manufacture. Moreover, for example when mounted in theaforesaid location L3, the module 400 is relatively inaccessible andneeds to function reliably without user intervention. Beneficially, themodule 400 utilizes aforesaid microeletronic mechanical systems (MEMS)technology, for example based upon silicon micromachining fabricationprocesses. The module 400 includes a battery 700 comprising one or moreelectro-chemical cells operable to provide electrical power, amongstother components, to a computer processor 710. A data memory 720including a software product is coupled in communication with theprocessor 710; the software product comprises software code which isexecutable upon the processor 710 and which is operable to coordinatefunctioning of the module 400. The processor 710 has associatedtherewith a clock (CLK) and an analogue-to-digital (A/D) converter forconverting analogue sensor signals to corresponding sampled sensor data;beneficially, the analogue-to-digital (ND) is based upon a high-speedmulti-channel sigma-delta type converter which exhibits modest powerconsumption. Sigma-delta converters are contemporarily employed inpower-critical devices such as miniature hearing aids which are batterypowered and need to function for long periods without attention, forexample for battery change. The module 400 further comprises ashort-distance wireless interface 730 for providing bidirectionalcommunication to and from the module 400; the wireless interface 730 isbeneficially implemented using contemporary Blue Tooth, Weebre orsimilar wireless interface technology operating pursuant to associatedstandardized communication protocol. The module 400 can alternatively beimplemented as a dedicated application specific integrated circuit(ASIC) including logic circuits.

The module 400 also includes an array of one or more sensors denoted by750 whose corresponding one or more outputs are coupled to the aforesaidND converter. Depending upon intended location, namely locations L1, L2,L3 and L4, and a degree of wheel monitoring functionality desired, thearray of sensor 750 includes one or more of:

-   (a) a pressure sensor 760 beneficially based upon a MEMS structure    including a silicon micromachined membrane with strain-gauge or    oscillatory resonant signal read-out;-   (b) a temperature sensor 765 for measuring an air or surface    temperature in proximity of the module 400, wherein the temperature    sensor 765 beneficially has a measuring range of −40° C. to +100°    C.;-   (c) an accelerometer 770 beneficially implemented in as MEMS    structure including one or more silicon micromachined proof masses    on a spring suspension with corresponding position readout for the    one or more proof masses indicative of acceleration; optionally, for    enhanced accuracy and response, the accelerometer is a    force-feedback type accelerometer; the accelerometer 770 is    beneficially sensitive to acceleration in one-, two- or three    orthogonal axes. For best monitoring of wheel 10 and associated tyre    30 operation, the accelerometer 770 is implemented as a three-axis    accelerometer;-   (d) a magnetic sensor 775, preferably implemented as a    vacuum-encapsulated reed relay switch but also susceptible to being    implemented as an Hall-effect device; the magnetic sensor 775 is    optionally included for activating the module 400 using a strong    magnetic brought into proximity of the module 400; however, as will    be elucidated in more detail later, other approaches to activating    the module 400 are also possible and are pursuant to the present    invention; and-   (e) a strain-gauge sensor 780 which is most potentially pertinent to    the module 400 when mounted at the location L3 onto the wheel 10.    The sensor 780 can be affixed to the tyre 30 prior to the tyre 30    being installed onto the hub 20.

Optionally, the module 400 is susceptible to including other types ofsensor not described in detail above.

Optionally, the battery 700 is, at least in part, a rechargeable batteryand provided with its own electro-magnetic recharging device actuated inresponse to rotation of the wheel 10 in operation, for example in amanner akin to an automatic wind-up mechanical wrist watch wherein wristmovement is operable to move an imbalance mass to provide watch-springwind-up energy. Alternatively, or additionally, piezo-electricrecharging of the battery 700 in response to rotation of the wheel 10can be employed.

In operation, the computer processor 710 is operable to performself-diagnostics and send a warning message via its wireless interface730 in event of partial or total malfunction occurring within the module400, and a confirmatory message sent when the module 400 is fullyfunctional; in an event that the module 400 malfunctions, its associatedvehicle is not immobilized, but merely results in reduced functionalityin respect of wheel and associated tyre monitoring. Beneficially, thedriver of the vehicle can be informed via the electronic control unit(ECU) regarding reduced functionality and provided with a choice whetheror not to continue driving despite malfunctioning of the module 400.

In operation, when the computer processor 710 detects that the signalsfrom the accelerometer 770 are substantially constant for more than apredefined time period, for example for a time period in a range from afew seconds up to 10 minutes, after cessation of a period of rotation ofthe wheel 10, the computer processor 710 is beneficially operable tocause the module 400 to assume a hibernating mode to conserve powerduring which the wireless interface 730 is substantially de-energized.During the hibernating mode, the computer processor 710 is beneficiallyoperable to periodically and momentarily activate the wireless interface730 for short periods to detect “wake-up” commands from the electroniccontrol unit (ECU) of the vehicle. As soon as the computer processor 710detects that signals from the accelerometer 770 and/or the pressuresensor 760 are temporally varying, for example during a pre-defined timeperiod, the processor 710 is operable to switch the module 400 to itsactive state, namely non-hibernating, with all its functional parts asshown in FIG. 14 brought into operation. Alternatively, or additionally,the module 400 can be explicitly set in a hibernating mode on receipt ofa specific hibernate instruction from the electronic control unit (ECU)950; beneficially, the specific instructions include the identificationcode (ID) of the module 400 which is to assume such a hibernating state;similarly, the module 400 can be explicitly instructed to assume afunctional active state, namely non-hibernating state, by receiving aspecific wake-up instruction from the electronic control unit (ECU) 950.Yet alternatively, or additionally, all the modules 400 included on thewheels 10 of the vehicle can be set to a hibernate state, or set to afunctional active state, by a general explicit instruction wirelesslytransmitted from the electronic control unit (ECU) 950; the generalexplicit instruction is beneficially sent by the electronic control unit(ECU) 950 in response to the driver of the vehicle starting and stoppinga combustion engine or an electric traction motor of the vehicle. Suchan electric traction motor is relevant when the vehicle has a hybridpowertrain or an electric power train provided with electric power fromfuel cells.

When considerable data processing is performed within the module 400 soas to distribute computing load around the vehicle, for example signalprocessing involving application of a Fast Fourier Transform (FFT) orsimilar signal processing algorithm, the module 400 is operable toreceive a synchronization signal for its given associated wheel 10derived from the aforementioned ABS sensor encoder 118 and itsassociated circuits associated with the given wheel 10. Such asynchronization signal is beneficially provided from the aforementionedelectronic control unit (ECU) 950 of the vehicle operating to provide adata communication hub for the vehicle. On account of the wheels 10 ofthe vehicle potentially revolving at mutually different rates, forexample when the vehicle is turning or due to slight difference inoutside diameters of the tyres 30, each wheel 10 and its associatedmodules need to be individually synchronized in respect of theirassociated ABS sensor encoder 118.

Data processing performed by the computer processor 710 is beneficiallycapable of reducing a volume of data to be communicated via the wirelessinterface 730 to the electronic control unit (ECU). Such local dataprocessing is of benefit in that it is primarily the wireless interface730 which consumes a majority of power from the battery 700 when themodule 400 is in operation. Data flow can be further reduced in themodule 400 by the processor 710 transmitting periodically at a beginningof time frames actual data values of sensor signals followed by datarepresenting changes in the data values during each time frame. Otherapproaches for obtaining data compression can also optionally beemployed to reduce power consumption at the wireless interface 730.Beneficially, the module 400 is operable to transmit accelerometersignal data and pressure P data at a maximum sample rate in a range of50 samples/second to 200 samples/second for each accelerometer axisand/or the pressure sensor 760 taking into consideration Nyquistsampling criteria. A lower rate of up to 1 sample per second fortemperature T is optionally employed on account of the temperature Tchanging less rapidly in comparison to the acceleration A and pressureP.

The module 400 is also beneficially operable to permit software updatesto be downloaded from the electronic control module (ECU) to the module400, for example via its wireless interface 730, for upgrading ormodifying its operation, for example in response to amended safetystandards or policy adopted by an operator of the vehicle. Such softwareupdates also enable new and improved data processing algorithms to belater employed, namely software upgrades.

As elucidated in the foregoing, the module 400 is programmed to have anidentification code (ID) which is useable by the aforesaid electroniccontrol unit (ECU) for distinguishing the module 400 from other similarmodules 400 on the vehicle, and also from similar types of modules 400on other vehicles which sporadically pass in near proximity, for exampleon an adjacent lane during motorway driving. The electronic control unit(ECU) is operable to use the identification code (ID) to identify fromwhich portion of the vehicle data conveyed via the module 400 isderived. Such identification will be described in more detail later.

The computer processor 710 in combination with its wireless interface730 is also operable to optionally provide a communication networkingfunction. Beneficially, the computer processor 710 has a directly wiredinterface so that a first module 400 mounted at the location L1 on thewheel 10 is capable of being directly coupled via a wire or opticalfibre communication link through the feed-through 310 as depicted inFIG. 7 to a second module 400 mounted at the position L2 on the rim 90within the volume 120 as depicted in FIG. 15 a. The processor 730 of thefirst module 400 located at the location L1 is thereby operable to:

-   (a) process signals generated by its array of sensors 750 and convey    the processed signals as processed data to its wireless interface    730 of the first module 400 for communicating to the electronic    control unit (ECU), as well as-   (b) receiving processed signals output from the second module at the    position L2 for conveying via the first module 400 and its wireless    interface 730 to the electronic control unit (ECU).

Alternatively, data signals from the second module 400 at the locationL2 can be:

-   (a) communicated via the wireless interface 730 of the second module    at the location L2 to the wireless interface 730 of the first module    at the location L1, and then-   (b) the data signals can be relayed via the wireless interface 730    its associated computer processor 710 of the first module 400 to the    electronic control unit (ECU).

Such a communication link is also susceptible to being used in reversefor conveying aforementioned ABS synchronization signals via the firstmodule 400 at the location L1 to the second module 400 at the locationL2 as depicted in FIG. 15 b.

In a similar manner, the second module 400 at the location L2 is able tofunction as a network relay for a third module 400 mounted at thelocation L3. Beneficially, the second module 400 at the location L2 iscoupled by wire or optical fibre via the feed-through 310 to the firstmodule 400 at the location L1, and the third module 400 at the locationL3 is coupled by wireless to the second module 400 at the location L2 asdepicted in FIG. 15 c. By such a configuration of FIG. 15 c, problemswith the mesh 210 and rim 90 functioning as a Faraday screen areavoided. Wireless communication between the third module 400 at thelocation L3 to the second module 400 at the location L2 is beneficial inview of a potentially large number of times the third module 400 at thelocation L3 moves in respect of the second module 400 at the location L2in response to flexure of the wall 230 of the tyre 30 as the wheel 10rotates in operation; wires or similar direct connections linking themodules at the locations L2 and L3 would not only be prone to breakagedue to work-hardening effects, but would also be impractical to attachonce the tyre 30 has been installed onto the hub 20 on account of thevolume 120 then being user-inaccessible.

In an alternative configuration, the third module 400 at the locationL3, mutatis mutandis for the module 400 at the location L4, iselectrically coupled to the mesh 210 of the tyre 30 which is used as ahighly effective patch radio antenna for communicating by wireless tothe electronic control unit (ECU). In such a configuration, the thirdmodule 400 at the location L3 is capable of function as a wireless relaynode for communicating data from the second module 400 mounted at thelocation L2 on the rim 90. Such a configuration is illustrated in FIG.15 d.

Other network configurations for the modules 400 at the locations L1,L2; L3 and L4 are also feasible. For example, the modules 400 areoptionally operable to all communicate directly by wireless via theirwireless interfaces 730 directly with the electronic control unit (ECU)as depicted in FIG. 15 e. Yet alternatively, the modules 400 aredynamically reconfigurable depending upon received wireless signalstrength at the electronic control unit (ECU), for example betweenvarious network modes as elucidated in the foregoing with reference toFIGS. 15 a to 15 e. Such flexibility to reconfigure a communicationnetwork provided by the modules 400 is beneficial when wheels 10 areswapped around or changed on the vehicle. Such adaptability will bedescribed in more detail later.

Beneficially, the first, second, third and fourth modules 400 mounted atthe locations L1, L2, L3 and L4 respectively each are provided withtheir uniquely-defining identification codes (ID) which the modules 400are operable to employ when communicating with the electronic controlunit (ECU) for distinguishing their data from that of other modules 400.Moreover, such identification codes (ID) are beneficial when theelectronic control unit (ECU) sends synchronization signals derived fromthe ABS sensor encoders 118, for example in a situation whereconsiderable data processing is performed locally at the modules 400 toreduce a quantity of data to be communicated via their wirelessinterfaces 730 to the electronic control unit (ECU) in operation.

In the foregoing, components such as the wheel 10 and its associated oneor more modules 400 and its electronic control unit (ECU) mounted on thevehicle have been described. These components form a part of a wheel-and tyre-monitoring system which will now be elucidated in greaterdetail with reference to FIG. 16.

In FIG. 16, there is shown in plan view the aforementioned vehicleindicated generally by 900. The vehicle 900 is driven in operation bythe aforesaid driver denoted by 910 in FIG. 16. Moreover, the vehicle900 comprises a front tractor unit 920 including a combustion engine 930operable to provide motive force to a pair of steerable front wheels 10beneficially implemented in a manner substantially as depicted in FIG.4. The combustion engine 930 is at least one of: a contemporary cylindercombustion engine, a combustion engine with turbocharger, an electricseries or parallel hybrid engine, a gas turbine engine, a fuel cellsystem providing electrical power to associated electric motor traction.The vehicle 900 also comprises a trailer unit 940 having two sets ofdouble rear wheels 10 as shown; the double rear wheels 10 arebeneficially implemented in a manner as depicted in FIG. 5 and areoptionally also steerable in a manner similar to the front wheels 10 ofthe front tractor unit 920. Other configurations of wheels 10 for thevehicle 900 are possible and FIG. 16 is merely one example fordescribing the present invention. The vehicle 900 is further providedwith the aforementioned electronic control unit (ECU) denoted by 950;the electronic control unit (ECU) 950 includes a computer processortogether with data memory and one or more wireless interfaces andelectrical interfaces, the computer processor being operable to executeone or more software products including executable software code. Theelectronic control unit (ECU) 950 is coupled in communication with aconsole 915 operated by the driver 910. Optionally, the electroniccontrol unit (ECU) 950 is also coupled in communication with thecombustion engine 930 for performing engine management and monitoringfunctions, for example deliberately limiting a speed, or recommending tothe driver a suitable speed, at which the driver 910 is able to drivethe vehicle 900 in an event of the electronic control unit (ECU) 950detecting a problem, or potential problem, with one or more wheels 10 ofthe vehicle 900. Moreover, the electronic control unit (ECU) 950 is alsowirelessly coupled to one or more modules 400 mounted on one or more ofthe wheels 10 of the vehicle 900 as elucidated in the foregoing.

The electronic control unit (ECU) 950 includes an antenna 960 fortransmitting and receiving wireless signals as denoted by 970 forenabling the vehicle 900 to communicate with other facilities, forexample a control centre 1000 of an enterprise organising logistics fora fleet of such vehicles 900, or to a service facility 1010 whereatwheels 10 and their tyres 30 of the vehicle 900 can be serviced orreplaced as depicted in FIG. 16. Beneficially, the electronic controlunit (ECU) 950 is operable to monitor operation of the wheels 10 of thevehicle 900 and automatically inform the control centre 1000 of a needto inform the driver 910 to drive the vehicle 900 into the servicefacility 1010 for servicing its wheels 10 and associated tyres 30, forexample as part of a delivery schedule planned for the vehicle 900,thereby causing less disruption to a service provided by the enterpriseto its customers. A visit to the service facility 1010 is optionallyinvoked in response to weather conditions or time, for example inconnection with exchanging summer tyres 30 to winter tyres 30 inNorthern Europe and North America.

Optionally, the electronic control unit (ECU) 950 is also wirelesslycoupled to a global positioning system (GPS) 1020 for determining inoperation a spatial position of the vehicle 900 upon the surface of theEarth. The GPS system 1020 is, for example, that managed by USAuthorities or an equivalent European Galileo positioning system. Yetalternatively, or additionally, the GPS system 1020 is based on a mobiletelephone, namely cell net, system known as GPRS or similar. Inoperation, the electronic control unit (ECU) 950 is operable todetermine whereat the vehicle 900 is located and convey this positionalinformation to the control centre 1000 so that the control centre 1000is aware of the position of the vehicle 900. Moreover, as elucidated inthe foregoing, in an event that electronic control unit (ECU) 950detects by way of one or more of the modules 400 that one or more of itswheels 10 are defective or needing maintenance, or are potentiallylikely to become defective or needing maintenance, the control centre1000 can direct the vehicle 900 to a suitable geographically convenientservice centre 1010. Optionally, the control centre 1000 is alsooperable to arrange, based upon knowledge of the position of the vehicle900, for the tractor 920 to be decoupled from its trailer 940 at asuitable geographical location so that an alternative tractor can berapidly coupled to the trailer 940 to haul the trailer 940 and itscontents further promptly to its destination, for example to a customer;the tractor 920 can then be serviced without disrupting time-criticaldeliveries in the trailer 940 to the customer. Moreover, the servicecentre 1010 can also be warned in advance, either directly from thevehicle 900 or indirectly via the control centre 1010 or both, regardingarrival of the vehicle 900 together with an indication of a likelyproblem with one or more wheels 10 of the vehicle 900. Such notificationof problems regarding the vehicle 900 to the control centre 1000 andoptionally to the service centre 1010 is susceptible to occurringautomatically without the driver 910 needing to interpret messages andactively inform one or more of the control centre 1000, the servicecentre 1010 or the customer. An improvement of service to the customeris thereby susceptible to being achieved.

In order that the vehicle 900 should not be immobilized in an event ofits electronic control unit 950 detecting a problem with one or more ofthe wheels 10 of the vehicle 900, or malfunction of one or more of itsmodules 400, the electronic control unit (ECU) 950 is operable togenerate various warning messages. In an event of malfunction of one ormore of the modules 400, the electronic control unit (ECU) 950 isoperable to send a warning to at least one of the control centre 1000and the driver 910 of such malfunction, but continue to monitor otherwheels 10 whose modules 400 are continuing to function correctly. Suchgraceful decline in monitoring functionality of the modules 400 mountedon one or more of the wheels 10 is susceptible to improving operationalrobustness of the vehicle 900, namely failure of one or more of themodules 400 does not immobilize the vehicle 900. It is a decision thenof the driver 900 and/or the control centre 1000 whether or not tocontinue driving the vehicle 900 in view of one or more of its module400 becoming non-operational. A potential cause of one or more of themodules 400 failing is exhaustion of batteries 700 therein, orreplacement of a tyre 30 for example.

2. Methods of Identifying Locations of Modules Pursuant to the PresentInvention

With regard to the present invention, the foregoing descriptiondescribes various apparatus and modules with which the present inventionis susceptible to being implemented. However, the present invention isconcerned with a method of identifying locations of wheel modulesincluded in wheels and/or their associated tyres; for example, to amethod of identifying locations of wheel modules operable to monitorcharacteristics of wheels and/or their associated tyres and conveyinginformation indicative of these aforementioned characteristics via acommunication link to an electronic control unit (ECU) and/or controlsystem, for example for user-display. Moreover, the present inventionalso concerns wheel modules for use in implementing aforementionedmethods; various implementations of these wheel modules have beendescribed in the foregoing and are also described in followingparagraphs.

It will be appreciated from FIG. 16 that the vehicle 900 has many wheels10, namely ten for the example described in the foregoing. When eachwheel 10 is provided with three modules 400 in its locations L1, L2 andL3, the vehicle 900 is potentially equipped with thirty such modules400; if more than one module 400 is included at each of the locationsL1, L2, L3 or L4, for example one module 400 at θ=0° and another atθ=180° for the location L2 in a radial disposition, there arepotentially even more than thirty such modules 400 present. In practice,certain of the wheels 10 are beneficially provided with fewer than threemodules 400 so that a total of around five to twenty modules 400, forexample ten modules 400, are conveniently employed altogether for thevehicle 900 for example. A problem arises in programming the electroniccontrol unit (ECU) 950 to recognize its respective modules 400 and havenecessary information regarding locations whereat the modules 400 arepositioned in the vehicle 900.

It is potentially extremely laborious, and potentially susceptible todata-entry error, for the driver 910, or person otherwise responsiblefor the vehicle 900, to have a list of the identification codes (ID) ofthe modules 400 together with their positions in the vehicle 900 andmanually input, for example by typing on a computer keyboard, suchinformation into the electronic control unit (ECU) 950. There thusarises a need to automatically locate, namely to “calibrate”, thevehicle 900 in respect of spatial disposition of its modules 400, namelyinform the electronic control unit (ECU) 950 regarding spatialdisposition of its modules 400. Such “calibration” is important forproviding the driver 910, the control centre 1000 and/or the servicecentre 1010 with correct information about which wheel 10 of the vehicle900 is potentially defective, potentially defective or needingattention, for example charging with compressed air to increase itspressure P or needing a tyre 30 change. Certain types of unbalancedefects or tyre wall 230 defects cannot be ascertained by mere casualvisual inspection of a wheel 10 and its tyre 30.

In a first method of identifying locations of modules 400 on the vehicle900, namely “calibrating” the vehicle 900, the driver 910, or personotherwise responsible for the vehicle 900, presses a key on a controlunit, for example on a keyboard of the console 915, coupled incommunication with the electronic control unit (ECU) 950 to indicatethat a module locating routine is about to be implemented. The driver910 or person responsible takes a permanent magnet and then walks alonga route around the vehicle 900 starting at a first predefined positionand ending at a second predefined position. When walking around theaforesaid route, the driver 910 or person responsible presents themagnet in close proximity to each wheel 10 in sequence along the routeso that the one or more modules 400 thereat are exposed to a magneticfield generated by the magnet. The route comprises, for example,starting at a front right corner of the vehicle 900 and moving in aclockwise manner around the vehicle 900 to a front left corner of thevehicle 900; mutatis mutandis for an anti-clockwise route around thevehicle 900. However, other routes are possible and are within the scopeof the present invention, for example addressing the front pair ofwheels 10 first and then progressing back along the vehicle 900eventually to the rear pair of wheels 10; mutatis mutandis for a routecommencing at the rear pair of wheels moving progressively eventually tothe front pair of wheels 10.

When moving around the route, the driver 910 or person responsibleundertakes at each wheel 10 to offer the magnet firstly in closeproximity to the axle 110 for activating the module 400 present at thelocation L1 and then moves the permanent magnet outwardly towards aperimeter of the wheel 10 for activating its one or more modules 400mounted at the locations L2, L3 and/or L4; mutatis mutandis for analternative starting at the perimeter of the wheel 10 inwards towardsthe hub 20 of the wheel 10. As an alternative to employing a permanentmagnet, an electromagnet can be employed which is momentarily energizedin close proximity to each wheel 10 along the route for executing thefirst calibration method.

The permanent magnet is operable to cause the magnetic sensor 775present in each module 400 to send a signal to its associated computerprocessor 710 which is in response operable to send a message includingthe identification code (ID) of the module 400 via its wirelessinterface 730 by wireless communication to the electronic control unit(ECU) 950. The electronic control unit (ECU) 950 thereby receives asequence of identification codes (ID) in an order corresponding to thepredetermined spatial route, and thereby is able to determine where themodules 400 are located in the vehicle 900. However, the electroniccontrol unit (ECU) 950 is susceptible to being provided with completelyerroneous data in an event that the driver 910 or person responsibledoes not diligently follow the predetermined route. In practice, thefirst method of “calibrating” the vehicle 900 is feasible to employ buttends to be tedious for the driver 910 or person responsible to executeand is also susceptible to abuse.

The inventors have appreciated that it is highly desirable to utilizemethods of locating positions of modules 400 on the vehicle 900 whichare less tedious and faster to execute in practice.

A method according to the invention of identifying locations of modules400 on the vehicle 900, namely “calibrating” the vehicle 900, will nowbe described with reference to FIGS. 17 a to 17 e. In FIG. 17 a, thevehicle 900 is illustrated in plan view with its front set of wheelsdenoted by 10 a, its middle set of wheels denoted by 10 b, and its rearset of wheels denoted by 10 c. The vehicle 900 is driven in a directionx towards an elongate substantially linear object 1100 placed upon aroad surface; the object 1100 is, for example, a substantially linearstraight calibration ridge implemented as an elongate rubber strip whichcan be temporarily deployed across the road for calibration purposes.

In the second method of identifying positions of modules 400 on thevehicle 900, namely “calibrating” the vehicle 900, the driver 910 inputsto the electronic control unit (ECU) 950 that the vehicle 900 is to becalibrated; for example, the driver 910 presses an appropriate key orbutton on the console 915. The driver 910 then drives the vehicle 900over the object 1100 as depicted progressively in FIGS. 17 b to 17 dcausing vertical acceleration signals A_(v) and/or momentary change inpressure P signals as depicted in FIG. 17 e to be received by theelectronic control unit (ECU) 950. In FIG. 17 e, an abscissa axis 1110denotes progressive movement of the vehicle 900 in the direction denotedby x, and an ordinate axis 1120 denotes change in vertical accelerationA_(v) or change in pressure P. On account of pulses in signals ofmodules 400 associated with the front wheels 10 a being received firsttogether with their identification codes (ID), the electronic controlunit (ECU) 950 is thereby capable of automatically associating the frontwheels 10 a to their corresponding modules 400 by way of theiridentification codes (ID). Moreover, on account of pulses in signals ofmodules 400 associated with the middle wheels 10 b being received nexttogether with their identification codes (ID), the electronic controlunit (ECU) 950 is thereby capable of automatically associating themiddle wheels 10 b to their corresponding modules 400 by way of theiridentification codes (ID). Furthermore, on account of pulses in signalsof modules 400 associated with the rear wheels 10 c being received lasttogether with their identification codes (ID), the electronic controlunit (ECU) 950 is thereby capable of automatically associating the rearwheels 10 c to their corresponding modules 400 by way of theiridentification codes (ID). However, the second method of “calibrating”the vehicle 900 does not enable the electronic control unit (ECU) 950 todistinguish on which side of the vehicle 900 the modules 400 arelocated.

A third method of identifying locations of modules 400 on the vehicle900, namely “calibrating” the vehicle 900, will now be described withreference to FIGS. 18 a to 18 e. In FIG. 18 a, the vehicle 900 isillustrated in plan view with its front set of wheels denoted by 10 aland 10 ar to denote left and right sides of the vehicle 900respectively, its middle set of wheels denoted by 10 bl and 10 br todenote left and right sides of the vehicle 900 respectively, and itsrear set of wheels denoted by 10 cl and 10 cr to denote left and rightsides of the vehicle 900 respectively. The vehicle 900 is driven in thedirection x at a non-perpendicular angle towards the aforementionedobject 1100 placed upon the road surface.

In the third method of identifying locations of modules 400 on thevehicle 900, the driver 910 inputs to the electronic control unit (ECU)950 that the vehicle 900 is to be “calibrated”; for example, the driver910 presses an appropriate key or button on the console 915 and alsoinputs an indication of which side of the vehicle 900 will first contactupon the aforesaid object 1100, namely either a left-hand-side or aright-hand-side of the vehicle 900. The driver 910 then drives thevehicle 900 over the object 1100 at a non-orthogonal inclined angle, forexample in a range of 50° to 85° wherein 90° corresponds to theorthogonal deployment as shown in FIG. 17, as depicted progressively inFIGS. 18 b to 18 d causing vertical acceleration signals A_(v) and/ormomentary change in pressure P signals as depicted in FIG. 18 e to bereceived by the electronic control unit (ECU) 950. In FIG. 18 e, theabscissa axis 1110 denotes progressive movement of the vehicle 900 inthe direction denoted by x, and the ordinate axis 1120 denotes change invertical acceleration A_(v) or change in pressure P. On account ofpulses in signals of modules 400 associated with the front wheels beingreceived first in a sequence 10 ar followed by 10 al together with theiridentification codes (ID), the electronic control unit (ECU) 950 isthereby capable of automatically associating the front wheels 10 ar, 10al to their corresponding modules 400 by way of their identificationcodes (ID), also noting on which side of the vehicle 900 the modules 400are mounted. Moreover, on account of pulses in signals of modules 400associated with the middle wheels being received next in a sequence 10br followed by 10 bl together with their identification codes (ID), theelectronic control unit (ECU) 950 is thereby capable of automaticallyassociating the middle wheels 10 br, 10 bl to their correspondingmodules 400 by way of their identification codes (ID), also noting onwhich side of the vehicle 900 the modules 400 are mounted. Furthermore,on account of pulses in signals of modules 400 associated with the rearwheels being received last in a sequence 10 cr followed by 10 cltogether with their identification codes (ID), the electronic controlunit (ECU) 950 is thereby capable of automatically associating the rearwheels 10 cr, 10 cl to their corresponding modules 400 by way of theiridentification codes (ID), also noting on which side of the vehicle 900the modules 400 are mounted. However, the second method of “calibrating”the vehicle 900 does not enable the electronic control unit (ECU) 950 todistinguish on which side of the vehicle 900 the modules 400 arelocated. The third method is an improvement upon the second method of“calibrating” the vehicle 900 but needs more input from the driver 910with a risk that the driver 910 incorrectly enters information regardingwhich side of the vehicle 900 contacts onto the object 1100 first.

As an alternative to employing the object 1100, the vehicle 900 cansimply be driven over a road curb or similar when implementing thesecond and third methods of identifying locations of one or more modules400 on the vehicle 900, namely “calibrating” the vehicle 900.

The second and third methods of “calibrating” the vehicle 900 areespecially appropriate for identifying the modules 400 at all fourlocations L1, L2, L3 and L4 when signals from the pressure sensors 760of the modules 400 are employed to provide signals as presented in FIGS.17 e and 18 e. On account of the modules 400 mounted at the location L3susceptible to providing acceleration signals as depicted in FIG. 10with pulses for each turn of their respective wheel 10, the second andthird methods are not optimal for identifying the positions of modules400 mounted at the third location L3 on the wall 230 of the tyre 30based upon acceleration measurements. There are however approaches toaddressing such an issue as will be elucidated later. However, thesecond and third method are certainly satisfactory for the modules 400mounted at the locations L1 and L2 based on acceleration measurements.

The methods, according to the invention as disclosed above, of“calibrating” the vehicle 900 are susceptible to being further improvedby adopting a following general “calibration” method:

-   (a) the driver 910 activates the electronic control unit (ECU) 950    to send out a message by wireless to all its wheels 10 and their    associated modules 400 to identify themselves; such a message is    beneficially, for example, sent out by the electronic control unit    (ECU) 950 each time the vehicle 900 is activated in case wheels 10    of the vehicle 900 have been modified whilst the vehicle 900 has    been stationary in a deactivated state. The modules 400 respond by    declaring their existence and their corresponding identification    codes (ID). The electronic control unit (ECU) 950 proceeds to store    a list or similar record of the identification codes (ID) in its    data memory;-   (b) the driver 910 then drives the vehicle 900 across a smooth road    surface substantially devoid of topographical features; the modules    400 mounted at the location L3, similar at the location L4, on the    wheels 10 will give rise to pulsating acceleration signals A_(z) in    a manner as depicted in FIG. 10 whereas the modules 400 at locations    L1 and L2 provide essentially non-pulsating signals, disregarding    gravitational g effects. The electronic control unit (ECU) 950    thereby identifies in the list or record of the identification codes    (ID) which modules 400 are mounted at the location L3 or L4 on their    respective wheels 10;-   (c) the driver 910 then executes one or more of the methods    according to the invention which clearly identify where the modules    400 mounted at locations L1 and L2 on their respective wheels 10 are    disposed in the vehicle 900; and-   (d) the electronic control unit (ECU) 950 then monitors the pulse    signals, in a manner as depicted in FIG. 10, from the modules 400    mounted at the location L3 or L4 on the wheels 10 and correlates the    number of pulses as depicted in FIG. 10 for a given time period of    travelling of the vehicle 900 with a number of revolutions of the    wheels 10 as determined by the ABS sensor encoders 118. On account    of slight mutual difference between the wheels 10, for example    effective external diameter, certain of the wheels 10 will have    executed more turns than others, allowing the correlation to    determine which modules 400 mounted at the location L3 correspond to    which of the wheels 10.

Steps of the aforementioned general method of “calibrating” and thefirst to sixth methods of “calibrating” the vehicle can be combined invarious different combinations to more reliably detect where the modules400 are located on wheels of the vehicle 10. Such methods aresusceptible to simplifying operation of the vehicle 900 and avoidingerror in comparison to the first method of “calibrating” the vehicle 900by magnetic activation.

3. Application of Wheel and Tyre Monitoring Pursuant to the PresentInvention for Vehicle Maintenance Purposes

Referring to FIG. 19, a potential operational situation encountered byan enterprise denoted by 2000 operating a fleet of the vehicles 900 fromits control centre 1000 with several service centres 1010 a, 1010 b,1010 c and collections of wheels 10 in reserve at the centres 1010 a,1010 b, 1010 c and/or depots 2010 a, 2010 b is that wheels 10 mounted onthe vehicles 900 and wheels 10 in storage at the service centres 1010and/or the depots 2010 potentially have mutually differentconfigurations of modules 400 mounted thereonto as depicted by variouscross-hatching patterns employed in FIG. 19. Moreover, certain of themodules 400 may also be configured with different combinations ofsensors; for example, some modules 400 will include pressure sensors 760and temperature sensors 765, whereas other modules will includeaccelerometers 770 and temperature sensors 765, and yet others willinclude a full complement of pressure sensors 760, temperature sensors765 and accelerometers 770. The accelerometers 770 are potentially one-,two- or three-axis accelerometers. Moreover, as an aspect of policy, theenterprise 2000 may be desirous to have certain defined configurationsof modules 400 on front wheels 10 a of its vehicles 900 and otherdefined configuration of modules 400 on rear wheels 10 b, 10 c of itsvehicles 900. Moreover, a configuration of modules 400 on any givenvehicle 900 is potentially dynamically altering as wheels 10 are removedfrom and installed onto the vehicles 900 as part of a maintenanceschedule adopted by the enterprise. Furthermore, certain modules 400 maypotentially occasionally fail due to their batteries 700 becomingexhausted. In view of such potential diversity as represented bydifferent shaping for the wheels 10 in FIG. 19, none of the aforesaidsixth methods of “calibrating” the vehicles 900 will be optimal in allcircumstances. In order to address such a complex situation, theaforementioned apparatus 600, 680, 690 is beneficially implemented in adynamically alterable manner in response to different configurations ofmodules 400 being available as determined by one or more of theaforementioned methods of “calibrating” the vehicles 900, or in responseto declared functionality as communicated from the modules 400 to theelectronic control unit 950.

Beneficially, when the modules 400 respond to the aforementioned messagesent out from the electronic control unit (ECU) 950 for the modules in agiven vehicle 900 to identify themselves, for example in step (a) of thegeneral method of “calibration”, the modules 400 respond by not onlydeclaring their identification code (ID) but also a description of theirfunctionality, namely an indication of their individual configurationsof sensors included therein, and optionally their capacity to executelocal data processing thereat. For example, certain modules 400 areoperable to respond with their identification codes (ID) together withinformation that they each have only a pressure sensor 760 and atemperature sensor 765, whereas other modules 400 are operable torespond with their identification codes (ID) together with informationthat they each have only a x- and y-axis accelerometer 770 together witha temperature sensor 765, and so forth for inclusion in theaforementioned list or record kept at the electronic control unit (ECU)950. The electronic control unit (ECU) 950 is thereby able todynamically select a most suitable method of “calibrating” the vehicle900 and inform the driver 910 on the console 915 accordingly. By theelectronic control unit (ECU) 950 being aware of the functionality ofits wheels 10, it is able to convey such information to the controlcentre 1000 for use in directing maintenance schedules for the vehicle900, for example sending the vehicle 900 to a service centre 1010 whichhas a suitable equivalent replacement wheel 10.

The enterprise 2000 therefore beneficially implements in its vehicles900 a general wheel monitoring method including steps as follows:

-   (a) establishing communication with one or more of its vehicles 900;-   (b) receiving information in response from electronic control    modules (ECU) 950 of the one or more vehicles 900 regarding    configurations of the module 400 on their wheels 10 and operating    status of the one or more wheels 10, for example whether the wheels    10 have developed imbalances or are loose;-   (c) determining for one or more of the vehicles 900 whether one or    more of their wheels 10 are in need of maintenance or replacement;-   (d) identifying one or more service centres 1010 having one or more    suitable replacement wheels for the one or more vehicles 900 in    step (c) having been found to require replacement, or having    facilities for performing maintenance on the one or more vehicles    900 in step (c) having been found to require maintenance; and-   (e) directing the one or more vehicles 900 found to require    maintenance or replacement of its one or more wheels 10 to one on    the one or more service centres 1010 for performing wheel    maintenance or replacement on the one or more vehicles 900.

The general wheel monitoring method described above is susceptible tobeing implemented automatically by way of computer-based supervisionfrom the control centre 1000 and/or from one or more of the servicecentres 1010. When implementing the method, the service centres 1010and/or the depots 2020 are operable to communicate their inventory ofwheels 10 in a dynamic manner. Moreover, the control centre 1000 is alsooperable to maintain dynamically a record of operational status of itsvehicles 900 at least in respect of their wheels 10 furnished with on ormore modules 400 pursuant to the present invention.

Adoption of the general wheel monitoring method is beneficial in thatsafety and reliability is improved which potentially may bring insurancepremium benefits for the enterprise 2000, as well as potentiallyenhancing the quality of their service to their customers.

4. Auto-Alignment of Modules Employable for Implementing the PresentInvention

As will be appreciated from the foregoing, the module 400 is employedwhen implementing the present invention in various configurations. Whenthe module 400 includes the accelerometer 770 as depicted in FIG. 14,the module 400 can be regarded as being a form of inertial navigationunit (INU). Moreover, it is elucidated in the foregoing that processingsignals corresponding to radial, tangential and transverseaccelerations, namely A_(y), A_(x) and A_(z) as depicted in FIG. 9, andresolving them to yield the vertical acceleration A_(v) as depicted inFIGS. 11 and 13 is found to be highly beneficial for deriving anindication of imbalance of the wheel 10, a type of imbalance of thewheel 10, whether or not the wheel 10 is skewed out of plane, whether ornot the wheel 10 is loose on its fasteners, as well as monitoringflexural characteristics of the walls 230 of the tyre 30. However, in amanner similar to inertial navigation units (INU) for steering vehiclessuch as rockets, helicopters, aircraft and so forth, it isconventionally found important that the inertial navigation units (INU)are mounted in accurate angular alignment with various reference axes ofthese vehicles. However, achieving such accurate angular alignmentrequires accuracy and precision which is potentially time consuming andcostly to achieve. In a similar manner, pursuant to the presentinvention, it is highly desirable that the one or more modules 400 bemountable to the wheel 10, for example at one or more of the locationsL1 to L4, without a high degree of mounting precision and accuracy beingnecessary. By implementing the present invention such that the module400 can be mounted in manner which does require its orientation to beprecisely ensured, time and costs associated with furnishing the wheelwith one or more of the modules 400 can be reduced. Such implementationof the present invention will now be elucidated with reference toexample embodiments of the invention.

For a given wheel 10 correctly mounted to its axle 110, it is beneficialto refer to:

-   (a) a lateral direction as being the z-axis parallel to the axis    B-B;-   (b) a radial direction from the axis B-B, and thus from the axle    110, as being the y-axis; and-   (c) a tangential axis at a given position on the wheel 10 as being    the x-axis,    as illustrated in FIG. 20.

The z-axis and the y-axis are pertinent at the locations L1 to L4. Thex-axis is dependent upon a radius rat which the point is from the axisB-B. FIG. 20 corresponds to FIG. 9 for the inclination angle φ beingsubstantially zero. As elucidated earlier, the acceleration A_(z) isespecially useful, as depicted in FIG. 10, for monitoring flexuralcharacteristics of the tyre 30 as well as detecting whether or not thewheel 10 is at a skewed angle relative to its axle 110. Moreover, thevertical acceleration A_(v) resolved from A_(x) and A_(y) accelerationcomponents measured at a given module 400 is beneficial for monitoringimbalance in the wheel 10 and also a type of imbalance involved.However, as shown in FIG. 20, the module 400 is potentially mounted inan angularly misaligned position on the wheel 10 such that its localorthogonal axes denoted by x′, y′, z′ do not align with true axes x, y,z required for generating highly useful A_(x), A_(y), A_(z) accelerationsignals.

Accelerations A_(x)′, A_(y)′, A_(z)′ correspond to measurements ofaccelerations along the local orthogonal axes x′, y′, z′ respectively.It is feasible to resolve the accelerations A_(x)′, A_(y)′, A_(z)′ inrespect of the true axes x, y, z as provided by a matrix mapping asdefined by Equation 10 (Eq. 10):

$\begin{matrix}{{\begin{pmatrix}1 & 0 & 0 \\0 & {\cos\;\beta} & {\sin\;\beta} \\0 & {{- \sin}\;\beta} & {\cos\;\beta}\end{pmatrix}\begin{pmatrix}{\cos\;\alpha} & {\sin\;\alpha} & 0 \\{{- \sin}\;\alpha} & {\cos\;\alpha} & 0 \\0 & 0 & 1\end{pmatrix}\begin{pmatrix}A_{x}^{\prime} \\A_{y}^{\prime} \\A_{z}^{\prime}\end{pmatrix}} = \begin{pmatrix}A_{x} \\A_{y} \\A_{z}\end{pmatrix}} & {{Eq}.\mspace{14mu} 10}\end{matrix}$wherein angles α and β are resolving angles mapping the axes x′, y′, z′onto the true axes x, y, z.

A special condition arises when the wheel 10 rotates at a constantangular velocity ω, for example as determinable by the electroniccontrol unit (ECU) 950 from signal generated from ABS sensor encoders118, the vehicle 900 is driving straight ahead and not turning, forexample as determined from an angular sensor coupled to the steeringwheel at the console 915, and a plane of the wheel 10 is orthogonal tothe axis B-B and hence to the axle 110 in that:

-   (a) the lateral acceleration A_(z) is substantially zero as define    by Equation 11 (Eq. 11);-   (b) the tangential acceleration A_(x) is substantially zero when    integrated over a complete 2π change in the rotation angle θ of the    wheel 10.

$\begin{matrix}{{\int_{\theta_{1}}^{\theta_{2}}A_{z}}\  = 0} & {{Eq}.\mspace{14mu} 11}\end{matrix}$wherein θ₁ and θ₂ are lower and upper integration limits correspondingto first and second angular rotation angles θ of the wheel 10.

$\begin{matrix}{{\int_{\gamma}^{\gamma + {2n\;\pi}}A_{x}}\  = 0} & {{Eq}.\mspace{14mu} 12}\end{matrix}$wherein γ is an offset angle and n is an integer such that n=1, 2, 3, .. .

Suitable values for the angles α and β are susceptible to being computedin an iterative manner so that Equations 11 and 12 can be substantiallyachieved, or at least a minimized condition in respect of the angles αand β is susceptible to being achieved. For example, spurious roadsurface noise present in the accelerations A_(x)′, A_(y)′, A_(z)′potentially requires a minimum condition to be searched for as a bestapproximation for satisfying Equations 11 and 12.

Optimal values for the angles α and β can either be found from anexplicit solution for Equations 10, 11 and 12, or iteratively byrecomputing for various combinations of the angles α and β for a sampleof signals representative of the accelerations A_(x)′, A_(y)′, A_(z)′until a nearest approximation to Equations 11 and 12 is achieved.

Computation of the angles α and β is beneficially performed at theelectronic control unit (ECU) 950. Alternatively, distributed computingperformed at the module 400 can also be employed for computing theangles α and β. Once the angles α and β have been computed for aminimized condition or a zero condition as given in Equations 11 and 12,application of these angles α and β pursuant to Equation 10 to obtainthe accelerations A_(x), A_(y), A_(z) for monitoring operation of thewheel 10, for example as depicted in FIGS. 11 and 13, is susceptible tobeing implemented at the electronic control unit (ECU) 950 or at themodule 400, or distributed between both the electronic control unit(ECU) 950 and the computer processor 710 of the module 400 to spreadcomputational load.

Equations 10 to 12 are an example of auto-resolving accelerations sensedby the accelerometer 770 of the module 400 to generate correspondingacceleration signals suitable for processing as depicted in FIGS. 11 and13 with associated description in the foregoing. Although auto-resolvingfor a three-axis accelerometer 770 is described, such approximateauto-resolving can be also be employed when the accelerometer 770 is atwo-axis accelerometer for example in simplified form. Auto-resolving isalso susceptible to being referred to as auto-alignment.

Auto-resolving, for example as described in Equations 10 to 12, is ofbenefit in that the one or more modules 400 mounted one or more of thelocations L1 to L4 do not need to be mounted onto the wheel 10 pursuantto highly precise angular alignment, thereby simplifying mounting of theone or more modules 400 to the wheel 10 and potentially reducingassembly and mounting costs.

When auto-resolving pursuant to Equations 10 to 12 is employed in theapparatus 600, a corresponding apparatus as indicated generally by 2200in FIG. 21 wherein an auto-resolver is denoted by 2210. The apparatus2200 includes at least one module 400 whose accelerometer 770 isoperable to generate the acceleration signals A_(x)′, A_(y)′, A_(z)′which are firstly auto-resolved in the auto-resolver 2210 to generatecorresponding resolved acceleration data for the accelerations A_(x),A_(y), A_(z). The resolved accelerations A_(x), A_(y), A_(z) are thenfurther resolved in the resolver 620 in respect of the rotation angle θof the wheel 10 as sensed by the ABS sensor encoder 118 to generatecorresponding vertical acceleration A_(v) signal data and alsoacceleration A_(z) signal data. The acceleration A_(v), A_(z) signaldata are then subject to harmonic analysis in the harmonic analyzer 630to generate corresponding series of harmonic coefficients Q_(v)(m) andQ_(z)(m) respectively in relation the angular frequency ω of rotation ofthe wheel 10. The harmonic coefficients Q_(v)(m) and Q_(z)(m) are thenoptionally subject to harmonic scaling in the scaler 640 to generatecorresponding scaled harmonic coefficients y_(v)(m)·Q_(v)(m) andy_(z)(m)·Q_(z)(m) which are then subject to analysis in terms ofabsolute magnitude and relative magnitude to determine whether or not:

-   (a) the wheel 10 is imbalanced;-   (b) a type of imbalance present in the wheel 10;-   (c) the wheel 10 is skewed in relation to the axle 110;-   (d) the wheel 10 is loose and wobbling about on its fasteners;-   (e) the tyre 30 has defects in its flexural characteristics, for    example its mesh 210 has become damaged;-   (f) the tyre 30 is insufficiently inflated;-   (g) the tyre 30 is over-inflated;-   (h) the tyre 30 is oval or has a higher-order lobed distortion;-   (i) there is a mass imbalance in the wheel 10;-   (j) wheel bearings associated with the axle 110 are vibrating or    rattling in an unexpected manner indicative of a fault, or    potentially developing fault,    to mention a few alternative types of analysis which are executable    using the apparatus 2200.

When harmonic scaling in the scaler 640 is optionally not required, itsscaling values are beneficially set to a uniform value, for exampley_(v)(m)=1, y_(z)(m)=1 unity value, or the scaler 640 simply bypassed.Moreover, for the apparatus 2200, one or more modules 400 can beoptionally mounted at one or more of the locations L1, L2 and L3. Theapparatus 2200 is susceptible to being implemented in hardware, insoftware executable on computing hardware, or a combination of suchhardware and software. Moreover, the apparatus 2200 is susceptible tobeing implemented substantially in the electronic control unit (ECU)950, on the module 400, or on both the module 400 and electronic controlunit (ECU) 950 in combination. The software is optionally supplied asone or more software products on one or more data carriers. Moreover,the software is optionally dynamically reconfigurable depending onpotentially changing configurations of one or more modules 400 includedon the wheel 10.

The apparatus 2200 illustrated in FIG. 21 is susceptible to beingmodified in a manner akin to the apparatus 690 illustrated in FIG. 13,namely concurrently or alternately being operable to harmonicallyanalyze a sampled signal representative of the pressure P in the volume120 of the tyre 30.

The auto-resolver 2210 requires calibrating in order to determine itscorrection angles α and β as elucidated in the foregoing. Suchcalibration is beneficially implemented as part of the aforesaid methodsof “calibrating” the modules 400, namely enabling the electronic controlunit (ECU) 950 to identify which modules 400 with which it is requiredto communicate on the vehicle 900, wherein the modules 400 are mountedat various locations on wheels 10 of the vehicle 900, with potentiallymutually different operating characteristics of the modules 400; aselucidated earlier, a situation potentially arises in operation wherecertain wheels 10 of the vehicle 900 are provided with a morecomprehensive set of modules 400 in comparison to other wheels of thevehicle 900, in a potentially temporally dynamically changing manner.Auto-resolving in the auto-resolver 2210 has an effect with regard tothe module 400 mounted at the location L3 to effectively set the offsetangle φ₀ in Equation 6 (Eq. 6) to substantially a null value, namelyφ₀=0, and thereby potentially simplifies associated signal processing inoperation for monitoring flexural characteristics of the tyre 30.

5. Applications of the Invention

Although use of the present invention in relation to heavy commercialvehicles is described in the foregoing, it will be appreciated that theinvention is also applicable to other types of vehicle, for example onwheels of aircraft, on wheels of automobiles, wheels of motorcycles andbicycles, on heavy construction equipment, on the wings of electricitywind turbines to identify potential structural problems, and so forth.

Expressions such as “has”, “is”, “include”, “comprise”, “consist of”,“incorporates” are to be construed to include additional components oritems which are not specifically defined; namely, such terms are to beconstrued in a non-exclusive manner. Moreover, reference to the singularis also to be construed to also include the plural. Furthermore,numerals and other symbols included within parentheses in theaccompanying claims are not to be construed to influence interpretedclaim scope but merely assist in understanding the present inventionwhen studying the claims.

6. Optional Modifications to the Invention

Modifications to embodiments of the invention described in the foregoingare susceptible to being implemented without departing from the scope ofthe invention as defined by the appended claims.

For example, use of the ABS sensor encoder 118 for sensing rotation ofthe wheel 10 has been described in the foregoing. However, additionallyor alternatively, a measure of the angular orientation θ of the wheel 10can also be computed, as elucidated in the foregoing, on a basis of thegravitational force g acting upon the accelerometer 770 of the module400. The gravitation force g is manifested in operation in theacceleration components A_(x), A_(y) and is superimposed on anyacceleration experienced at the wheel 10 due to general acceleration ordeceleration of the vehicle 900. On account of a typical time scale inwhich cyclical fluctuations of the gravitational force g as observed inthe acceleration components A_(x), A_(y) being generally more rapid thaneffects due to such general acceleration or deceleration, it is feasibleto filter out or compensate for such components in the accelerationcomponents A_(x), A_(y) as a weight of the vehicle 900 and a motivepower output from the engine or motor 930 of the vehicle 900 can beestimated or measured. When the angular orientation θ of the wheel 10 isderived from the acceleration components A_(x), A_(y), in addition to oras an alternative to the ABS encoder sensor 118, such derivation doesnot preclude the use of aforementioned auto-alignment of the axes x′,y′, z′ of the module 400 to the true x, y, z axes of the wheel 10representative of orthogonal tangential and lateral axes respectively,see FIG. 9. Such derivation of the angular orientation θ enables thepresent invention to be, for example, applied to vehicles which are notequipped with ABS braking or partially equipped with ABS braking on onlycertain of their wheels. Moreover, such derivation enables the presentinvention to be retrofitted in certain situations to older vehicleswhich are not provided with ABS braking.

Flexure of the side-wall 230 of the tyre 30 is also susceptible to beingsensed by a first module 400 mounted at the location L3 moving inrespect of a second module 400 mounted at the location L2 in closespatial proximity to the first module 400. In operation, flexure of theside-wall 230 causes a relative spatial distance between the first andsecond modules 400 to vary correspondingly.

In a first configuration, the first module 400 is provided with a sourceof radiation, and the second module 400 is operable to monitor amagnitude of a portion of the radiation received thereat and convey acorresponding signal by wireless to the electronic control unit (ECU)950. The signal is representative of a change of spatial separationbetween the first and second modules 400 as a function of their wheel 10rotating.

In a second configuration, the second module 400 is provided with asource of radiation, and the first module 400 is operable to monitor amagnitude of a portion of the radiation received thereat and convey acorresponding signal by wireless, for example using the mesh 210 of thetyre 30 as a wireless patch antenna, to the electronic control unit(ECU) 950. The signal is representative of a change of spatialseparation between the first and second modules 400 as a function oftheir wheel 10 rotating.

The radiation can be at least one of: a substantially constant magneticfield generated by a permanent magnet, an alternating magnetic field,ultrasonic radiation, wireless radiation, pulsed optical radiation,capacitive electrostatically-coupled radiation to mention a fewexamples. Ultrasonic radiation is beneficially generated and receivedusing piezo-electric transducers.

The invention claimed is:
 1. A method of identifying locations of one ormore modules of an apparatus included in a vehicle for monitoringoperation of at least a front set of wheels and a rear set of wheels ofthe vehicle, the sets of wheels including a left and a right wheel, theone or more modules operatively mounted to revolve with the sets ofwheels, the one or more modules being operatively coupled incommunication with a processing arrangement of the vehicle, the one ormore modules being operable to sense at least one physical parameter ofthe wheel and to generate at least one corresponding sensor signal forthe processing arrangement, the processing arrangement being operable toprocess the at least one sensor signal to compute information indicativeof operation of the sets of wheels, wherein the method includes: (a)arranging for at least one elongate feature to be extending at anon-orthogonal inclined angle relative to a direction of travel of thevehicle; (b) driving the vehicle over the elongate feature to cause thesets of wheels, together with its associated one or more modules, tocontact momentarily onto the elongate feature and communicating signalsincluding signal components stimulated by contact of the sets of wheelsonto the elongate feature to the processing arrangement, the signalsidentifying a time at which their wheels contacted onto the elongatefeature and one or more identification codes of the one or more modulesmounted onto the sets of wheels; and (c) from a temporal sequence of thesignals received at the processing arrangement, identifying locations ofthe sets of wheels of the vehicle whereat the one or more modules arelocated, characterized in an additional step of identifying those one ormore modules mounted to a wall or onto an inside rim of a tire of the atleast one wheel by identifying periodic pulses in acceleration signalcomponents derived from the one or more modules corresponding torotation of the at least one wheel.
 2. A method as claimed in claim 1,wherein the apparatus includes a sensor arrangement for sensing anangular orientation of the sets of wheels.
 3. A method as claimed inclaim 1, wherein the signals are indicative of at least one of: (d) oneor more components of acceleration sensed at the at least one wheel; and(e) a pressure sensed in a tire of the sets of wheels.
 4. A method asclaimed in claim 1, wherein the vehicle is driven at a transverse angleso as to result in signals from the one or more modules being temporallymutually different between corresponding left-hand-side andright-hand-side wheels of the vehicle, thereby enabling the processingarrangement to distinguish locations of the one or modules along thevehicle and distinguish whether the one or more modules are located on aleft-hand side or a right-hand side of the vehicle.
 5. A method asclaimed in claim 1, the method being implemented repetitively whilst thevehicle is being driven.
 6. A wheel-monitoring apparatus including ofone or more modules for monitoring operation of at least a front set ofwheels and a rear set of wheels of the vehicle, the sets of wheelsincluding a left and a right wheel, the one or more modules operativelymounted to revolve with the sets of wheels, the one or more modulesbeing operatively coupled in communication with a processing arrangementof the vehicle, the one or more modules being operable to sense at leastone physical parameter of the wheel and to generate at least onecorresponding sensor signal for the processing arrangement; theprocessing arrangement being operable to process the at least one sensorsignal to compute information indicative of operation of the sets ofwheels, the processing arrangement being operable to receive signals,including signal components stimulated by contact of the sets of wheelsonto an elongate feature extending at a non-orthogonal inclined anglerelative to a direction of travel of the vehicle, the signalsidentifying a time at which their wheels contacted onto the elongatefeature and one or more identification codes (ID) of the one or moremodules mounted onto the sets of wheels; in that the processingarrangement is arranged to identifying locations of the sets of wheelsof the vehicle whereat the one or more modules are located from atemporal sequence of the signals received at the processing arrangement;and in that the processing arrangement is arranged to identify those oneor more modules mounted to a wall or onto an inside rim of a tire of theat least one wheel by identifying periodic pulses in acceleration signalcomponents derived from the one or more modules corresponding torotation of the at least one wheel.
 7. A vehicle including awheel-monitoring apparatus as claimed in claim 6 operable to monitoroperation of at least one wheel of the vehicle pursuant to a method ofidentifying locations of one or more modules of an apparatus included ina vehicle for monitoring operation of at least a front set of wheels anda rear set of wheels of the vehicle, the sets of wheels including a leftand a right wheel, the one or more modules operatively mounted torevolve with the sets of wheels, the one or more modules beingoperatively coupled in communication with a processing arrangement ofthe vehicle, the one or more modules being operable to sense at leastone physical parameter of the wheel and to generate at least onecorresponding sensor signal for the processing arrangement, theprocessing arrangement being operable to process the at least one sensorsignal to compute information indicative of operation of the sets ofwheels, wherein the method includes: (a) arranging for at least oneelongate feature to be extending at a non-orthogonal inclined anglerelative to a direction of travel of the vehicle; (b) driving thevehicle over the elongate feature to cause the sets of wheels, togetherwith its associated one or more modules, to contact momentarily onto theelongate feature and communicating signals including signal componentsstimulated by contact of the sets of wheels onto the elongate feature tothe processing arrangement, the signals identifying a time at whichtheir wheels contacted onto the elongate feature and one or moreidentification codes of the one or more modules mounted onto the sets ofwheels; and (c) from a temporal sequence of the signals received at theprocessing arrangement, identifying locations of the sets of wheels ofthe vehicle whereat the one or more modules are located, characterizedin an additional step of identifying those one or more modules mountedto a wall or onto an inside rim of a tire of the at least one wheel byidentifying periodic pulses in acceleration signal components derivedfrom the one or more modules corresponding to rotation of the at leastone wheel.
 8. A tangible data carrier comprising a non-transitorysoftware product recorded on the data carrier, the product beingexecutable on computing hardware for executing a method of identifyinglocations of one or more modules of at apparatus included in a vehiclefor monitoring operation of at least a front set of wheels and a rearset of wheels of the vehicle, the sets of wheels including a left and aright wheel, the one or more modules operatively mounted to revolve withthe sets of wheels, the one or more modules being operatively coupled incommunication with a processing arrangement of the vehicle, the one ormore modules being operable to sense at least one physical parameter ofthe wheel and to generate at least one corresponding sensor signal forthe processing arrangement, the processing arrangement being operable toprocess the at least one sensor signal to compute information indicativeof operation of the sets of wheels, wherein the method includes: (a)arranging for at least one elongate feature to be extending at anon-orthogonal inclined angle relative to a direction of travel of thevehicle; (b) driving the vehicle over the elongate feature to cause thesets of wheels, together with its associated one or more modules, tocontact momentarily onto the elongate feature and communicating signalsincluding signal components stimulated by contact of the sets of wheelsonto the elongate feature to the processing arrangement, the signalsidentifying a time at which their wheels contacted onto the elongatefeature and one or more identification codes of the one or more modulesmounted onto the sets of wheels; and (c) from a temporal sequence of thesignals received at the processing arrangement, identifying locations ofthe sets of wheels of the vehicle whereat the one or more modules arelocated, characterized in an additional step of identifying those one ormore modules mounted to a wall or onto an inside rim of a tire of the atleast one wheel by identifying periodic pulses in acceleration signalcomponents derived from the one or more modules corresponding torotation of the at least one wheel.